The answer is in thermodynamics and kinetics. These two are arguably the most important concepts to grasp in chemistry.

But sometimes, even after several years of basic chemistry education, it is not easy to form a clear picture on how they govern reactivity!

Tutorial Review: Contents and Introduction

In this tutorial, we will try to introduce and summarize what these two concepts are, and their implications in chemical reactivity. This is obviously an introduction, intended for chemistry students of all levels.

For sure, there are more comprehensive explanations out there, and if you want one, go grab any of the best-known general chemistry books, or a more specific organic chemistry textbook. However, we have found that there are not many short explanations out there available for the general scientific public. This is somehow worrying, since, without a basic understanding of thermodynamics and kinetics, there is no way to understand the basic principles of reactivity. And without understanding reactivity, you are missing out on the most important part of chemistry.

But if you really want to dive on physical chemistry concepts as such, unfortunately you will find that most books can be impenetrable without a basic understanding of maths, physics and chemistry itself.

This is what we want to fix with this short tutorial. To give you a general overview on why chemical compounds react. We want to break the gate-keeping that has always been going on with physical organic chemistry!

As mentioned, this is intended to be brief. We will start off with the basic definitions, and hopefully make you go all the way through to understanding free-energy profiles of catalytic reactions.

Interested yet? Keep reading!

• A quick disclaimer: Since my background is in organic chemistry, I will base the explanations on simple organic chemical reactions, but most of the general principles apply to any kind of chemical reactivity.
• For most energy diagrams, the energy values are orientative, made up in order to explain the concepts.

Thermodynamics: The Energetic Stability of Molecules

Thermodynamics is the branch of physics that deals with heat, work and temperature, and their relation to energy, radiation, and physical properties of matter.

That is the definition of thermodynamics. As you can see, it is an incredibly broad concept. Let’s forget about it for now. How does thermodynamics dictate why do chemicals react?

Well, imagine every different molecule having an associated value for energy.

Some molecules will have larger energies and some others lower energies. Then consider that every chemical system has the tendency to go towards the point of lowest energy possible, in effect, the most stable point. This means that a molecule with high energy (less stable) will have a tendency (or “will want to react”) to transform into another molecule with lower energy (more stable).

Why is that? Because the process of going from a high energy state to a lower energy state releases energy, or heat, in what is called an exothermic process. This is what we call a thermodynamically-favored process, and it is basically what the laws of thermodynamics are telling us.

Thermodynamic Stability in Energy Diagrams

This is easier than it might sound. The image below illustrates what you just read. Molecule A can react in two ways: Absorbing heat it can be transformed into 1. Alternatively, it can evolve into 2 by releasing energy, in a thermodynamically-favorable manner. Of course, if these were the only two possible scenarios, all molecules of A would react to give 2, and stay there forever. But the picture is usually not that simple, and we will come back to this later.

You might be looking at the picture above and still not get what we mean by higher or lower energy. Let me redraw it in a way you will probably have seen elsewhere, or been taught in school/college:

The scheme above resembles what you are always taught in introductory organic chemistry courses: more substituted isomers of alkenes are more stable (A and 2 vs. 1) and trans isomers are more stable than cis isomers (2 vs A).

What does this means? It means that, given the appropriate circumstances or conditions, both 1 and A would like to react to give 2. But we now that less stable alkenes such as 1 are perfectly inert, and can be handled and stored without worries. So, what is the deal here?

The answer is kinetics and activation barriers.

Kinetics: The Barriers of Chemical Reactivity

Before diving into kinetics, let me present another quick example of a thermodynamically-favorable process. An energy diagram of an Sn2 substitution reaction in this case.

As you can see, if we set the zero in energy for a hydroxyde anion plus a chloromethane molecule (in energy diagrams you always set an energy for the whole system, not individual molecules), the total energy of the products of the corresponding Sn2 reaction (tert-butyl alcohol and a chloride anion) will be lower (about 20 kcal/mol lower!).

What does this mean? That the reaction is thermodynamically favorable, and in principle it will not take place the other way around.

But does this mean that, mixing hydroxide with chloromethane at any temperature will lead to the immediate formation of tert-butyl alcohol and chloride? Of course not! The rate at which the reaction proceeds will depend directly on the temperature, and if the temperature is low enough, the reaction will not take place at all, even though the process is thermodynamically favorable.

Why is that? Kinetics is the answer.

What Are Chemical Reaction Kinetics?

Chemical or reaction kinetics is the branch of physical chemistry that studies the rates (or speeds) of chemical reactions.

In summary, thermodynamics determines in what direction a chemical reaction proceeds, and kinetics determines the speed or rate at which that process occurs.

Of course, in the last scheme of the previous section, there was something missing. In a chemical reaction, reactant A does not simply transform into product B. Reactions take place through what we call transition states.

Transition states are intermediate structures between reactants and products of a chemical reaction step. They are usually higher in energy (less stable) than both the reactants and the products, and the energy difference between the reactants and the transition states, also known as activation energy, is the barrier necessary to overcome for a thermodynamically-favorable reaction to take place.

Why Do Chemicals React? Thermodynamics and Kinetics Combined

See below a now complete version of the free-energy diagram of the Sn2 substitution reaction. As you can see, the process is thermodynamically favorable, but a barrier or activation energy of 23.0 kcal/mol has to be overcome in order to reach the products.

The larger the activation energy, the lower the speed or rate of a reaction at any given temperature. Usually, we set a limit of barriers of around 25 kcal/mol for reactions to proceed at a significant rate (this is, in several hours or days) at 25 ºC. Easy enough to remember.

Stability vs Inertness

No matter how thermodynamically favorable a process is, if the barriers to reach the corresponding transition are too high (say, higher than 30-40 kcal/mol), that chemical reaction is not going to take place under regular conditions.

This allows us to make a clarification between stability and inertness as properties of chemicals.

Stability is a thermodynamic concept, while inertness is a kinetic concept.

• A compound is stable, if it is relatively low in energy (compared to the molecules to which it may interconvert into). The opposite would be unstable, high in energy.

• On the other hand, we say that a compound is kinetically inert if in order to react it has to overcome large activation barriers.

A compound can be both unstable and inert. That is why we can handle and store thermodynamically unstable primary alkenes such as 1-propene without them isomerizing to more-stable secondary alkenes such as cis- or trans-2-propene (see the first two schemes).

But we can trick kinetics! Catalysts can be used to lower the activation energy of chemical transformations, allowing them to proceed more rapidly, or simply to proceed at all!

• Note: Theoretically, no matter how high the activation energy of a process might be, we say that it is always taking place at a certain rate. However, if the energy barriers are higher than, say, 50 kcal/mol, the rate or speed of the reaction would be so low that it would take many many years before we can detect a significant conversion.

Catalysis: Lowering the Barrier!

Now that we know why chemicals react, let me explain how we chemists try to override the system and make activation barriers lower.

A catalyst is a chemical entity (a molecule, a salt, a coordination complex…) which speeds up a chemical reaction. It also can unlock new reactivity pathways and make reactions work that would not be possible otherwise.

Let’s take a specific classical example. The electrophilic aromatic substitution of benzene with molecular bromine (Br–Br). This reaction is traditionally carried out using a Lewis acid as catalyst, such as iron tribromide.

But let us imagine first a catalyst-free version of the process, which I am certain can occur if you mix together benzene and bromine, and heat it up enough.

How Thermal, Catalyst-Free Reactions Occur

The first step of this reaction is the formation of the well-known Wheland intermediate. An intermediate (not to be confused with a transition state, which rather connects intermediates together) is a reactive chemical species which is formed in one of the steps in the middle of a chemical reaction of A leading to B, as intermediate point. For benzene to be transformed into bromobenzene, it has to pass through this intermediate species. Intermediates can rarely be isolated, since they usually are both thermodynamically unstable and kinetically reactive.

In any case, the reactants have to overcome a high activation barrier of 30 kcal/mol. Once the temperature is enough for this to take place, the rest of the process has lower activation barriers, and takes place downhill to give reaction products in an overall thermodynamically favorable process (exothermic by -11 kcal/mol).

But we can speed things up with a catalyst!

Lewis Acid-Catalyzed Electrophilic Aromatic Substitutions

By adding a catalyst to the mixture, we can access new transitions states, which are more stable, and hence lower in energy. And what happens when the transition state of the rate-limiting step of a reaction is lower in energy? That the activation barrier of the whole process is much lower!

This is basically the role of FeBr₃ (the catalyst) of this reaction: stabilizes transition states and intermediates. Now the activation barrier to reach the first transition state is much lower (20 vs 30 kcal/mol), allowing the reaction to take place under mild conditions.

Also, note that FeBr₃ is recovered unreacted with the products. This is another feature of catalysts: they can be recovered and re-enter another reaction cycle. This is why they are often employed in sub-stoichiometric amounts (this is, less than one mole of catalyst is enough to drive full conversion of one mole of starting material).

But as we have already mentioned, thanks to catalysis we not only can lower activation barriers that would need totally unpractical temperatures. We can also unlock reactions that would take hundreds of years to complete by themselves. We can also achieve completely new selectivities, and develop new chemical processes.

I work in catalysis myself, and I can tell you this is one of the most important, exciting and active fields of chemistry.

This is the end of this tutorial review, and I hope it has helped you to get a clearer picture of why chemical reactions take place and what leads chemicals to react. We certainly covered concepts you have to master if you are learning chemistry at any level!

The post Why Do Chemicals React? Kinetics and Thermodynamics appeared first on Chemistry Hall.

There is so much to this science that it can be hard to even know where to start! That’s why we put together this guide with recommendations for how to learn chemistry, plus tons of useful resources no matter what your level is.

What exactly is this guide?

Obviously you won’t learn chemistry reading this blog post by itself. This is more of a pedagogical article. However, we will point you towards tons of resources for learning this science, no matter if you are just a chemistry enthusiast or a college student.

This is a general introduction for approaching chemistry, from any level.

There is a very specific way of thinking that helps tackling the problems that chemistry has to offer. We will base our guide upon that cornerstone.

And you will find out what this theme is pretty soon if you keep reading.

An Introduction to Chemistry

But first, a quick introduction to the study of chemistry, what it is, and why you should make the effort to learn this awesome science.

What Is Chemistry?

Chemistry can be defined as the study of matter and the changes it undergoes. You’ll sometimes hear it called the central science because it is the connection between physics and all the other sciences, starting with biology. All that makes it sound abstract and esoteric, but really, chemistry is all around us. It wouldn’t be a stretch to say that it governs every aspect of your life.

Are you sitting inside? You’re surrounded by building materials that are structurally sound because of how chemistry holds them together. Reading this outside? Every living plant you see is consuming CO2 and releasing oxygen in the process of photosynthesis. The food you eat, the products you use to clean your house, the fuel you put in your car, the very air you breathe—it’s all chemistry.

What’s really incredible about chemistry is the seemingly infinite variety of stuff around us and the fact that it’s all just combinations of around 100 chemical elements. In reality, most of what we interact with in everyday life is made up of far fewer. When two or more of these elements are combined in a compound, the properties of the compound can be amazingly unlike the constituent elements. Would you guess that the table salt in your kitchen is made up of a chemical weapon and a metal that causes an explosion when it touches water?

What is Chemistry Used for?

It should come as no surprise, then, that chemistry is used for just about anything you can imagine. Life itself relies on chemistry, but humans have been harnessing it for our own benefit for thousands of years, knowingly or not. From our first combustion reaction (making fire) to the latest cutting-edge medical technology, this science has changed our lives in ways that are mind-blowing.

Long before we knew any scientific concepts that we take for granted today, we were performing basic chemistry. Some of the most important examples from the ancient world are processes that we still use today, such metallurgy and extracting compounds from natural sources, e.g. plants.

Many people consider alchemy to be the forerunner of modern chemistry. This is debatable, but regardless, the discipline that tirelessly sought a way to turn lead into gold fell out of favor among intellectuals right about the time when something closer to modern chemistry was beginning to catch on. The earliest publications in chemistry as a proper science date to the 16^th and early 17^th centuries.

Now, a few hundred years later, the field has positively exploded, with numerous subdisciplines. Today, we say that the five major branches of chemistry are general chemistry, organic chemistry, inorganic chemistry, biochemistry, and analytical chemistry. But there are tons of more niche areas of chemistry, too, like physical, materials, and nuclear chemistry, neurochemistry, chemical engineering, medicinal chemistry and pharmacology… The list goes on and on because chemistry is used for everything!

Why Should I Learn Chemistry?

So, aside from the fact that it is used for practically everything in life, why should you learn chemistry? There are tons of reasons!

Even if you don’t plan on a career in science, you’ll pick up a lot of useful skills and knowledge when you learn chemistry. Studying science helps you understand important issues, like climate change or food additives, more objectively. Chemistry is also great for developing problem solving skills.

More specifically, knowledge of chemistry unlocks some of life’s most profound mysteries… like how to make sure your baked goods come out moist and fluffy! Seriously though, it can make many routine tasks—like cooking—easier, and more importantly, it can help keep you safe. Knowing which cleaning products are okay to be used together and which should never be mixed is possible with chemistry, as is understanding how certain medicines work in your body, and much more.

This video sums it up really well:

Besides, chemistry is not a profession which seems to be going anywhere soon. Careers and jobs in chemistry, especially in research, are usually pretty fun, and creativity-driven.

Now that you’re convinced that you want to learn chemistry, how do you do it?

How to Learn Chemistry

I talked with many people that have studied chemistry, like myself, and everyone seems to have learnt this science very similarly.

There is a way of reasoning and thinking about chemistry which is common in chemical education.

Chemistry is an empirical science, so it is based on explaining observations, and taking what you extract from those observations to extrapolate and make predictions about other phenomena.

You can explain extremely simple chemistry questions, such as differentiating organic and inorganic compounds, to very complex scenarios with this same methodology.

This way of reasoning is, in my opinion, the best way to tackle chemistry problems. This goes from a kid learning basic science to a professional chemistry PhD working on ground-breaking research.

How to Rationalize, Explain and Extrapolate

To illustrate this, we will use a simple example:

First an observation: We observe that water freezes at a certain temperature (0 ºC at atmospheric pressure).

Then, rationalization/explanation: Thanks to previous knowledge, we can explain this observation in simple terms saying that at lower temperatures, molecules vibrate less, and can pack in a more efficient manner. The way water molecules can pack below 0 ºC, gives it a solid state structure.

We can generalize this to any other substance: Depending on how strong are intermolecular interactions between each molecule of a given substance, they will be able to pack in a solid state form more easily (at higher temperature).

Then we extrapolate to other systems/molecules: intermolecular forces between hexane molecules are much weaker (dispersion forces) than between water molecules (hydrogen bond). This will make it harder to pack them in a solid state structure, thus making its melting point much lower (-95 ºC, to be exact).

And this turns out to be true, as we can easily validate by determining (or consulting) the melting point of hexane.

And this can be made as simple as that or as complex as you would like your model to be.

This way of thinking fits perfectly with chemistry. That’s why I highly recommend it.

If you already took chemistry courses, you are probably familiar with this reasoning process, even if you didn’t really notice.

Where to Find Any Resource for Learning Chemistry

So you are already packed with a clear thinking process that you can adopt for tackling chemistry.

What do you need now?

Of course, you need information. Information is everything. You need books, resources and materials to study.

Well, we have good news for you! We live in the age of information technologies, and you can find literally everything anywhere. You can order a textbook from almost anywhere, and even find electronic versions of those books. You can find scientific research articles from home. You can visit Wikipedia and take a quick look about any subject you want. You can Google whatever you want and find tons of resources to learn from…

One might say, that there’s too much information out there! More than you can handle!

But I really don’t think there’s such a thing as ‘too much information’. Not if you are good at searching through it, and filtering what’s important. And this is a basic yet overlooked skill in our age. Focus on learning how to process, select and filter! And this not only applies to chemistry, but to every subject out there.

To be completely honest, even in 2020, I don’t think there is a better way to learn a natural science such as chemistry than starting from a good textbook.

Not get me wrong, there is plenty of info about chemistry. Heck, probably most of the university level course materials can be found in Google.

However, there is nothing like the great and didactical organization of a textbook. You can get one for your level, and when you are done going through most of it, you will be a master on that level. Of course, I encourage you to expand every topic that is not clear enough, or not covered deeply enough. For this purpose, or for a quick outlook, the internet is amazing.

There are plenty of different textbooks for any level. Which one is the best for me? What are my options? This is what we will cover next.

We strongly recommend you to navigate this site through the links on each section to check specific details and thorough comparison data.

The Best Books to Learn Chemistry at Any Level

No matter what your interest or level in this subject may be, there’s a great book out there to help you learn chemistry. This section won’t be too extensive, but you can find detailed write-ups on all of the books below in other posts.

Kids and Casual Learners

Our recent post on the best chemistry-themed gifts included three books that are a great fit for older kids or adults who have a casual interest in the central science.

Elements: A Visual Exploration of Every Known Atom in the Universe is visually stunning and chock full of cool information. It contains gorgeous photos and fun facts, and it would be an excellent introduction for people who are curious to learn about the chemical elements that make up our universe.

Ask a Science Teacher: 250 Answers to Questions You’ve Always Had About How Everyday Stuff Really Works is a book that is less focused on chemistry specifically, but which has still got tons of fascinating explanations in plain English. It’s a great book to show all the practical ways in which science affects us every day.

Chemistry for Everyone: A Helpful Primer for High School or College Chemistry is exactly what it sounds like. It’s definitely the most educational of the books in this section, although it is not intended to replace a complete chemistry course. We would recommend picking this up before taking your first chem class so that you have an idea of what to expect.

High School

We have two favorites when it comes to books for high school chemistry students. You can read more in our post on these and other high school chem textbooks, but here are our top picks in a nutshell:

Chemistry: Concepts and Problems: A Self-Teaching Guide is, of course designed for self-taught students. This makes it ideal if you end up in a class with a “teacher who doesn’t teach”, as students often report. It’s based on the programmed learning method for maximum learning effectiveness.

Chemistry for Dummies tracks a typical introductory chemistry course, making it suitable for high school and college intro to chem classes. No matter what your current level is, you can learn chemistry with this book.

We also published a separate review for the best chemistry books for self-study, which can be suitable for anyone, but especially to people at the high-school level.

University Level

At the university level, there are several types of chemistry courses you could be taking, each with its own separate textbook. Or, if you’re curious to learn chemistry but don’t need the credit to graduate, you could use one of these books to teach yourself!

If you’re learning General Chemistry, we’ve got a whole post dedicated to the best books for this class. But in the interest of time, our two top picks are Brown’s Chemistry: The Central Science and Tro’s Chemistry: A Molecular Approach. Both are top-notch textbooks, with the second one being a bit more expensive but also more accessible for most students, especially visual learners.

For people with a serious interest in learning chemistry, the next course is usually Organic Chemistry, or o-chem. Your professor has likely listed a book on their syllabus, but in our opinion, the best textbook to learn organic chemistry is Clayden’s Organic Chemistry. According to research, students value clarity above all else in textbooks, and this one is very easy to follow with plenty of practice problems. We also try to publish resources in which reaction mechanisms are well explained, here is an example with the Swern oxidation!

Your o-chem professor will probably also require or suggest you get a molecular modeling kit. This is highly recommended, even if it isn’t mandatory in your class. But remember, it doesn’t do any good to buy a kit if you don’t use it, so make sure you take full advantage of all the concepts it can help you understand.

By the time you get to Inorganic Chemistry, you’ve likely made a major commitment to studying chemistry. There are several inorganic chemistry textbooks that can help you learn more effectively, but our preference is Housecroft & Sharpe’s Inorganic Chemistry. It’s got just the right balance of detail and being easy to understand with very instructive graphics.

Two other main fields of chemistry are not forgotten. Here you can go and check for the best physical chemistry textbooks and the best analytical chemistry books.

Other important subfields such as biochemistry and electrochemistry are not left behind.

Also, it is mandatory that you start learning how to properly take notes in the form of a laboratory notebook, and writing good lab reports.

Online Resources

Apart from books, the second best resource for finding resources is clearly the internet. But what sites should I visit?

Of course, there are many university websites with plenty of information, but the easiest and quickest way find something, is of course, a search engine such as Google. But make sure to check what kind of site are you visiting, and if the information they provide is reliable. Many times, your query will take you to university sites that you can trust. But as we advised before, learning how to filter information is key!

As for other great websites to look for information, some of them are:

Wikipedia: Some criticize that anyone can edit it and write any information. This is true, but it is also true that it undergoes continuos review by experts, and inaccurate or undocumented information rarely goes unnoticed. The info sources or citations are usually great and often refer to original research.

Youtube: Just the same as Google, just search anything you want and you will most likely find a channel explaining everything about it to you! An example for Organic Chemistry is presented by Crash Course here.

As an example of this, we have collected some of the best chemistry lectures and conference talks in another article.

SciFinder and Reaxys: Professional scientific databases. They are paid tools, but if you study or work in a research institution, you will most likely have access to a subscription. These are great for looking through original research, and if you are serious about doing a career on chemistry, you’d better get used to playing with them!

Libretexts: Great repository for completely open access books online, which might not be accessible anywhere else. Lot’s of chemistry material there to find!

This list could go on forever, for example, our own place, Chemistry Hall, has plenty of resources to discover. But we really want to remark how important is to master search engine searches to look for exactly what you are looking for.

We will now finish with an important section for students: tips on taking on some of the most popular standarized chemistry exams in the US.

Taking Standardized Chemistry Exams

The single best thing you can do to prepare for most standardized exams is to take practice tests that are as similar to the real thing as possible. In addition to that, check out these tips for some of the major standardized chemistry exams.

Tips for AP Chemistry Exams

The AP chem exam is a college credit exam for high school students, so it literally pays to be prepared for this one. Your first step should be to buy one of the best AP chemistry review books, preferably one with lots of practice test so that you’ll feel comfortable with the structure of the exam and the formats of the different types of questions.

When taking your practice exams, make sure you do it under simulated testing conditions. Most of all, that means that you need to time yourself. Another important thing to keep in mind is that the topics that are covered on the exam are changed from time to time, so if you buy a review book, make sure it’s the most recent edition.

Similarly, make sure you get the latest version of exam logistics, such as when you will be allowed to use a calculator, the provided equation sheet, etc. And if your handwriting looks like chicken scratch, remember that your free response questions are being graded by humans, and doing your best to keep things legible could save you some points by making your grader’s life easier.

Tips for the SAT Chemistry Subject Test

Many colleges and universities do not require SAT II exams, i.e. subject tests, but they can be useful to present yourself as a better applicant. Usually, students are advised to take one science SAT subject exam and one humanities, and the SAT Chemistry Exam is one of the most popular science tests.

It should come as no surprise that your first step to success is to buy a chemistry SAT subject textbook. But it’s also important to realize that not all review books are created equal. There is one specific type of question on the SAT Chemistry Exam that is quite different from what most students are used to. They are called “relationship analysis”, and they can be confusing at first, so you need to make sure that your practice exams contain this type of problem.

When taking practice tests, always do it as close to real-life testing conditions as possible. That means setting a timer and being aware in advance of the things that are and aren’t allowed on exam day. For example, you are NOT permitted a calculator on the chemistry SAT II. If your algebra and basic math skills aren’t strong, it’s best to start working on them as far in advance of exam day as you can.

You will, however, be given a very basic periodic table of the elements. It wouldn’t be a bad idea to review periodic trends, groups, series, etc. and make a “brain dump” of all this information as soon as you are allowed to begin the test.

Tips for ACS Exams

Some college professors opt to give the American Chemical Society general chemistry or organic chemistry exam as their course final in lieu of preparing their own. This sounds like a terrifying prospect to lots of students, but it can actually be a blessing because you will be able to prepare yourself for it with more confidence.

Since the ACS exam is standardized, you can know in advance exactly what topics will be covered, the sorts of questions they tend to ask, etc. You can find official study guides and practice tests online, along with the rules for the test, provided materials, and so on.

We recommend that you start prepping well in advance so that you can space out the material and take your time with everything. Remember that active forms of studying, like doing practice problems or trying to explain concepts to someone else, are much more effective than just reading and rereading notes.

The ACS finals are cumulative, which means they are more about breadth than depth in terms of material. You can choose to go back to the beginning of your course work and study chronologically, or take a more tailored approach and first focus on material that you have a good, but not great, understanding of, before continuing on to any parts that make you feel hopelessly lost.

Tips for MCAT, PCAT, etc.

Pre-professional exams, like the MCAT and PCAT, are designed to measure your knowledge and aptitude in multiple subjects. On the MCAT, one section is called Chemical and Physical Foundations of Biological Systems, while the comparable section on the PCAT is Chemical Processes (there is a separate section for biology).

The names of these sections give you a clue as to what you are expected to know on each exam. Understandably, there is a greater focus on chemistry in this section for pharmacy students and more of a biology focus for med school.

The two exams have totally different structures and rules, so you need to get all that information as soon as you can so that you know how to study and prepare. For example, the PCAT is now given on the computer at a testing center with a calculator built into the exam in the chemistry section and others. However, calculators are not allowed on the MCAT chemistry section, so part of your test prep may include practicing doing calculations by hand.

As with other exams, you’ll greatly improve your chances of getting into med school or pharmacy school if you make use of a good review book with plenty of practice problems.

Time to Learn Chemistry!

If you follow this guide and make use of the resources at your disposal, you’ll be well on your way to learning chemistry. Now, all you need is to dedicate some time to daily study—consistency will make the difference in how far you go!

The post How To Learn Chemistry at Any Level appeared first on Chemistry Hall.

If you want to become a synthetic chemist, or you are planning to ace an experimental course on organic chemistry, TLC is something you really need to master.

So, what is this tutorial about? What am I going to learn if I continue reading?

Well, I am a synthetic organic chemist with years of experience in the lab, and I have run thousands of TLC and flash columns in any solvent combination that you can imagine. I also enjoy sharing and reading lab tricks with colleagues, or even online. You could say that there are very few things that I still don’t know about this technique.

What I decided to do, is to put together all my knowledge in this tutorial article, so you can start reading without knowing what a TLC is, and finish up by being able to separate and identify (almost) anything you want in an organic chemistry lab!

This guide is for many different levels.

I can tell you that even if you have never been in a chemistry lab before, you will be prepared to do a thin layer chromatography just by continuing to read the first sections.

On the other hand, I can also promise you that even if you have PhD in organic synthesis, there is still some tricks or hacks to learn in this guide.

Considering this, you can navigate this tutorial page by using the index shown right below. Happy TLCing everyone!

What is Thin Layer Chromatography?

You might be familiar with what chromatography is, but maybe you din’t know that, as a matter of fact, the name “chromatography” comes from some early experiments on thin layer chromatography.

The word chromatography comes from the Greek chroma, “color”, and graphein, “to write”. It was a technique to separate substances that had different colors.

Basically, a chromatography is any lab technique in which we separate different chemical components of a mixture by their affinity to a stationary phase (usually silica gel in TLC) and to a mobile phase (the solvent or mixture of solvents). They don’t necessary have to be colored compounds, since there are many other ways to detect or identify them.

Initial experiments on TLC allowed separating pigments of plant’s extracts. These pigments (such as chlorophyl) have different colors, and elute at different rates through the stationary phase, so they can be separated and easily visualized:

Chromatography can get very complex, with complicated and expensive instruments such as GC-MS or HPLC, but the most basic, most important and oldest technique is thin layer chromatography, or TLC.

In TLC, we use a stationary phase (most frequently silica gel) which is deposited over a glass or aluminum support. We then can spot mixtures of compounds over the same line. Then we elute the TLC with an organic solvent, and the different compounds will move upwards at different rates, allowing the separation of the different components.

What Is Thin Layer Chromatography Used for?

Thin Layer Chromatography is a cheap, quick and easy technique to separate components of a mixture. It is used by synthetic chemists to monitor chemical reactions and purifications.

And How Does a TLC Work?

Well, a TLC plate is an aluminum plate coated by a “thin layer” of a stationary phase, which is usually (>95% of the time in organic synthesis) silica gel.

Around 1 cm above the bottom of the plate, you can spot a solution of a mixture of compounds of different polarity.

Then, you “elute” the plate. you basically put it vertically inside a closed chamber which contains an amount of an appropriate solvent mixture. The solvent flows slowly up the plate through capillary action.

The stationary phase, silica gel contains Si–O–H bonds that bind to the different compounds of the mixtures in a variable manner depending on the polarity of the compounds. Also, depending on the nature of the solvent used (more polar or less polar), it will pull upwards some compounds faster than others.

In general, more polar compounds will “climb” slower up through the TLC plate, and less polar ones will fly upwards.

Then you just need to check how many and where in the TLC plate each spot is. Each spot corresponds to a different chemical compound on the mixture.

Usually you will need a UV (Ultraviolet) lamp to visualize the different spots, but if the compounds are strongly colored, as in the picture above, you can easily see the different components of the mixture.

How Do You Run a TLC? Step by Step Guide

1. Cut Your Plate

First you need to cut a piece of TLC plate of the appropriate size. What is the appropriate size? It depends on the purpose of the TLC, and how many spots you need to separate. If you just want to take a look on how many compounds you have in a mixture, one spot is enough.

TLC plates are generally made of aluminum coated by the stationary phase, and can be cut with scissors. Sometimes, the supporting material is glass and you will need a glass cutter to do the job.

Usually, a thin layer chromatography plate is around 5–7 cm high, and a line is drawn around 0.5–1.0 cm from the bottom. That is the line in which you will spot your mixtures to separate. It is important that you spot the mixtures above the solvent level on your elution chamber!

Also, remember to leave some separation between each spot at the bottom spotting line (so they don’t mix to each other!) and also leave a similar separation (of around half a centimeter) from each edge of the TLC plate.

2. Spot Your TLC

Then is time to prepare the samples of the mixtures to separate, and spot them on the TLC plate.

For simplicity, let’s start off with just a single spot, in which we will put a solution of a mixture of several compounds.

First we need to prepare a solution of our mixture. The usual average concentration of these solutions is a few miligrams of mixture/compound in around 0.5–1 mL of solvent. Those few miligrams are totally approximate. Just add a spatula or Pasteur pipette tip and dissolve it in a bit of solvent!

Once you got the solutions prepared (in this case, just the one!), it’s time to spot it on the bottom line of the TLC. You need to use a capillary tube (see the corresponding section for details). Take up some mixture solution with the capillary tube and press it lightly into the corresponding marked spot (use ALWAYS a pencil to mark in a TLC! Pen ink will elute with organic solvents, pencil graphite will not!) at the line around 0.5–1 cm above the bottom of the TLC.

Try to spot your mixtures as tightly as possible. Make very small spots of sample. Very wide spots will make the different compounds overlap leading to a not so nice separations. Maybe even some compounds will be hidden since those will be basically co-eluting with other massive spots. Generally speaking, more diluted and smaller spots are they way to go.

3. Elute the TLC Plate

Then is time to elute the plate. For this you need an elution chamber. There are commercial options, as the one in the picture below, specific for that purpose.

But you can use any glass container that you can cap, actually. A beaker works. A a clean jam jar will also do the job!

Then you need to fill it with about 0.5 cm height of the desired solvent system.

There is no absolute best starting point for selecting a solvent system. However, a extremely quick summary would be:

• If you are working with absolutely apolar organic molecules (no polar functional groups, only C and H), such as naphthalene, start with pure pentane or hexane.
• If you want to separate a compound with one or two mildly polar functional groups (ether, ketone, ester…), go for a 4:1 hexane/EtOAc mixture.
• If your molecule has one or two very polar groups (alcohol, amine, etc), go for 1:1 hexane/EtOAc.
• If your molecule is much more polar than that (e.g. a sugar, an amino acid…), swap hexane for DCM, and keep EtOAc as polar component. Use a 1:1 ratio for starters.
• If your compounds are so polar that do not move at all from the baseline with DCM/EtOAc, go for 9:1 DCM/MeOH or even 9:1 EtOAc/MeOH.
• If none of this works, you are looking at a extremely polar compound and you might want to consider using reverse phase (an apolar stationary phase, instead of silica gel)

If you want more details about choosing a solvent system, check the corresponding section below!

This being said, it is important that the solvent level is below the initial point where you spot your samples! Otherwise, they will get diluted and you will not get a clean separation.

Once the chamber is ready, just put in the TLC inside, vertically, and wait for the solvent to go up by capillary action. Take out the TLC plate when the solvent level is around 90% form the top (don’t let it drown!)

Before the plate dries, mark the eluent front (the line on the plate the solvent level has reached). You will need this to determine the retention factor (Rf) of each spot/compound.

Then, dry off the plate (with compressed air, blowing air, or just waiting…)

4. Visualize the TLC: Check Out the Results!

Finally, visualization. This is a matter of finding the right way to visualize the spots corresponding to each compound in the mixture you just separated.

If they are strongly colored (as in the picture above), you are good! You don’t need anything else, just look directly at the plate.

Most of the times, organic compounds will not be visible, but they will absorb UV radiation. So you just use a UV lamp. Finally, there are a lot of staining solutions that can be used to develop the plates and easily tell where each compound appears. Scroll down to the corresponding section to known more about visualization.

5. Determine the Retention Factor of the Different Compounds

What is Retention Factor?

In thin layer chromatography, retention factor (Rf) is the distance that a compound travels through the stationary phase (TLC plate) between the origin spot and the distance the solvent front moved above the origin.

To calculate the value of the Rf, you just have to apply this simple formula:

Rf(spot) = (distance the spot has moved)/(distance solvent front moved)

A visual example:

After eluting a mixture of benzaldehyde and benzyl alcohol in a TLC plate using 7:3 pentane/diethyl ether as a solvent, the two compounds travel a certain distance.

Benzaldehyde is less polar than the corresponding alcohol, so it is easily identifiable as the top spot.

After measuring the distance that both of the spots traveled, we can determine the retention factor for each compound in that solvent mixture. Simply divide the distance that one spot has traveled by the total distance the solvent has moved from the origin spot line.

For example, for benzaldehyde, it moved 3.2 cm from the origin. The solvent from has moved a total of 5 cm. So we can say and report the Rf of benzaldehyde in 7:3 pentane/diethyl ether to be 3.2/5 = 0.64.

Please, keep in mind that retention factors depend greatly on the solvent system used and on the stationary phase of the TLC. If you modify any of those, Rf will change. That’s why when reporting retention factor values, it is essential to specify those parameters for each compound.

6. Re-run the TLC with a Better Solvent System if the First Attempt Was not Successful

Finally, something that is very common while working with new compounds: Many times the first choice of solvent system will not be the appropriate, and maybe all the compounds of the mixture eluted together to the top of the TLC, or just didn’t move from the base spot, or maybe they are somewhere between, but still the separation is not perfect.

In any of these cases, you just have to keep tweaking the solvent system until you find the most suitable for your mixture!

It is not uncommon to run 3-4 TLC plates of a reaction crude (even for experienced chemists) before starting a flash column chromatography purification.

And that is pretty much what you really need to know to perform a TLC experiment. The only thing left is knowing which solvent system you need to separate your mixture appropriately, and to know what are the real-life applications of TLC.

Was anything not clear?

Don’t worry, a video is worth a thousand words! Check out this video guide for TLC:

A Quick Infographic Guide for Thin Layer Chromatography

After lining up the entire procedure for running a TLC, I want to cut to a quick reference graphical guide that we prepared.

It is the most visual way to sum up TLC technique that we could think of, and here it is for you:

Please, feel free to link, share and use this infographic as you please!

From this point, the introduction is finished.

We will get first into the main basic uses of TLC. Then we will move onto more details into each component of the technique. Then we will cover more advanced uses and techniques, such as prep TLC, 2D TLC, or flash chromatography.

And then we will finish with some mind-blowing tips and tricks and TLC troubleshooting.

Keep reading!

Thin Layer Chromatography for Reaction Monitoring

The main use of TLC is monitoring chemical reactions.

In a chemical transformation, you usually have a starting material (SM) that will get consumed to give rise to a product. In most cases, this product will have a different polarity than the SM. This means that they will have different retention factor in TLC, and you will be able to separate them by TLC.

You generally want a solvent mixture that gives both compounds a retention factor between 0.2 and 0.8. But of course, the main idea is that you can see both spots resolved, not together, so you can see if you still have SM in your reaction mixture or if it is all consumed. This would mean that the reaction is finished in most of the cases.

The trick is to make three spots on the TLC, one with the SM, another one with the reaction mixture (RM), and another one in the middle (co-spot or cross-spot) in which you put both a solution of the SM and the reaction mixture. This way you can clearly visualize, after elution, that your SM actually reacted to form a new product. This is particularly important if both SM and product have very similar Rf, and it is difficult to see if you actually have a new product or just SM in the reaction mixture.

As you can see in the diagrams below, it is very easy to see whether a reaction didn’t work at all (yet), if a product is being formed, but the reaction is not finished, or if all SM has been consumed and there are only products on the RM.

Furthermore, if you happen to have a sample of the reaction product that you want to obtain (because maybe you had run the same reaction before, or because it is a commercially available product), you can add another spot for the product, and another for a co-spot of both product and reaction mixture. This way you can confirm that the desired product has been formed.

TLC for Column Chromatography Purification

The second most typical scenario in which you are gonna have to use thin layer chromatography is while working on a flash column chromatography purification.

What Is Column Chromatography?

Column chromatography is a method for separating and isolating chemical compounds in the lab on a preparative scale, depending on its relative polarity.

The basis are exactly the same than for TLC. We have a glass column filled with a stationary phase (also usually silica gel).

On top of the stationary phase, we put the mixture of compounds that we want to separate. When we are trying to isolate one product from a reaction mixture, we call this mixture “crude product”.

Then, we pass solvent through the column, from the top to bottom, sometimes aided by applying pressure (this is what we call “flash column chromatography”). This makes the different compounds of the mixture elute through the stationary phase at different rates.

Then, the different fractions that come out of the bottom of the column are collected in different test tubes. If the separation was performed correctly, we will have each compound of the mixture in different test tubes. The we can just get rid of the solvent by evaporation and we will have our product pure.

The rate of elution for each compound depends on its retention factor (i.e. its polarity) in that particular solvent system. This means, they will come out of the column in the same relative rate rate as their spots eluted in a TLC.

How Do We Use TLC for Column Chromatography?

Well, first of all, before running a flash column chromatography, we need to select what is the appropriate solvent system for the purification. We do this by using TLC.

Ideally, the product(s) that we want to isolate, should have an Rf (retention factor) of around 0.4 in a given eluent (mixture of solvents) to allow for a smooth column purification.

The following image on the left illustrates how an ideal TLC for purification should look like. As you can see, two products are clearly visible and separated. So the solvent mixture that yields this result on TLC, will be a great choice for running the big scale column chromatography purification.

The images on the right, illustrate how this separation does proceed using that same solvent system. As you can see on the far right, the first compound leaves the column completely separated from the other one. It can be collected, and concentrated in vacuum, getting your product completely pure and dry!

TLCing the Fractions from Column Chromatography

But after running the column chromatography, you usually end up with dozens of tubes filled with eluent with the different compounds dissolved. Now we have to use TLC again!

As you can see, we spotted all the fractions/test tubes on the TLC, and eluted in the same solvent system. As you can see, we have two different products (spots) that came out of the column pretty close.

From fraction 5 to 10, we only have compound one, pure. We can mix these fractions, concentrate them, and we will have pure compound 1.

Fractions 11 and 12, have a mixture of the two compounds. Usually we throw away this kind of mixed fractions (unless we don’t actually care about the impurity, maybe it just doesn’t affect the next step of our synthesis!).

Fractions 13 and 14 have pure compound 2. If we also need this compound, we will just concentrate them together as well.

As you can see, TLC is extremely important for both reaction monitoring and product purification, the two cornerstones of any synthesis laboratory.

Checking What’s on Each Fraction with Other Techinques

Sometimes TLC is just not enough and you don’t know what compound/product is in each of the different fractions that came out of your flash column. Evaporating everything and taking an NMR is really time consuming, so you might want to go for an alternative technique if it’s available to you.

If you have access to a GC-MS (gas chromatography-mass spectrometer) or LC-MS (liquid chromatography-mass spectrometer), you can analyze quickly all the different fractions, and know the molecular mass of the compound(s) present on each of them.

Another cool instrument is the TLC-MS. This technique is usually much less available in chemistry labs than GC-MS or LC-MS, but if you can use it is great. Basically this machine automatically scraps off individual spots on an eluted TLC, and makes an MS analysis, so you can check the molecular masses present on of each spot of the TLC in usually less than a minute.

A Comment on Retention Factors and Flash Column

Using an eluent which gives an Rf of 0.4 for your compound is the usual rule of thumb, but it has of course many exceptions. If you have two compounds that are very close together in Rf, this might not be enough. Having two compounds show as two separate spots in TLC doesn’t mean that they will come out separately from flash column.

Column bands are like much much wider TLC spots, especially as we scale up the purification. Imagine that typical TLC that you overload with sample and you get two big unresolved overlapping spots. That is a closer picture to what is actually happening in your column chromatography.

For this reason, sometimes an Rf of 0.4 will not do the trick. If spots are separated by less than 0.15 Rf, you will usually need to be a bit more conservative and choose an eluent in which they have a retention factor of around 0.3, or even a bit less. Another cool trick to enhance this kind of purification is using thicker columns, this helps a lot with separation. Using longer columns doesn’t usually help, since you are just thickening the bands and making them overlap more!

On the flip side of the coin, sometimes your compound of interest just flies on TLC using certain solvent mixture, giving an Rf of 0.7-0.9. This might allow for extremely easy and fast separations in a couple of the first tubes/fractions.

In Depth Guide: Materials for Thin Layer Chromatography

Making Capillary Tubes

You will have to spot reaction mixtures, or reference samples in your TLC using capillary tubes.

You can either buy them, or make them yourself. This depends on your lab’s budget, but I don’t think there is much harm in buying some good capillary tubes. The commercial ones I use on a daily basis, usually last for months before breaking, if you are careful enough.

But you can make thin capillary tubes out of thicker glass tubes, you just need to heat them up and then pulling. For this, you can either use thicker capillary tubes or glass Pasteur pipettes.

Explaining the method for heating and pulling will sound more complicated than it actually is, just take a look at this short but on-point video:

As you can see is not terribly complicated, and it can even be a nice experiment for undergraduate labs. Just be careful with the flame (or other heating source that you use! Avoid using open flames in the lab if you have alternatives).

Elution Chambers for TLC

So, there are actual chambers designed for running TLC, and they are just great, such as these from Fischer:

But that doesn’t mean you need one of those fancy pieces of glasswares to run a TLC. The beauty and simplicity of this technique is that you can use it in basically any situation!

A typical temporary solution, if you are in a rush, is just using a beaker covered with something (like a watch glass, or even aluminum foil), so the solvent doesn’t evaporate and allows for a nice saturated atmosphere

It is worth mentioning here that this is another key for a good eluent chamber: You need the atmosphere as saturated as possible. This way, the solvent doesn’t evaporate on its way up through the plate, which would cause an uneven movement of the eluent front. This can be detrimental for the separation, so always ensure that your chamber is a reasonably closed system.

As you can see in the picture above, you can also put a piece of filter paper inside the chamber a while before eluting your TLC.

Why? The solvent will ascend through the filter paper as well (by the same principle than through the TLC), helping a lot in saturating the atmosphere inside the chamber with the eluent. This will make the eluent go up the TLC plate in a much more even manner.

Also, be patient, leave the eluent in the chamber with the filter paper for a while before eluting you plate!

Finally, the more practical low-cost alternative, in my opinion, is just using a glass tar with a screw cap, like the ones you get you jam, or other edible stuff in!

I survived through my undergrad labs and also through my first research experience only by using these “ghetto-chambers” on a daily basis!

Alternative Stationary Phases

As we were saying, more than 95% of the cases you will perform a TLC in plates coated by silica gel as stationary phase.

But there are very specific cases in which different stationary phase may be considered.

Silica gel (SiO2) is slightly acidic, so certain compounds are quite sensitive to these acidic conditions. In those cases, you can first try to neutralize the silica gel adding a basic solvent to your eluent (typical conditions are adding 2-5% of triethylamine to your solvent mixture).

Many times this does the trick, but in other cases is not enough. For those cases, there are alternative stationary phases such as neutral alumina (Al2O3). Maybe your target compound does survive in alumina and you can use it for both TLC and flash column chromatography purification.

Another alternative stationary phase is reverse phase.

Typical silica gel stationary phases are very polar, and you elute the plate with a solvent systems that is (much) less polar than SiO2. This works wonders form most typical organic compounds.

However, if you are working with extremely polar molecules, you will find that they get stuck into the SiO2 like crazy and no matter how polar you make your eluent, they simply won’t move.

For these cases, we can use reverse phase chromatography, in which the stationary phase is apolar (it will retain polar compounds much less), and you will use polar solvents, such as MeOH, as eluent. Very polar compounds, such as oligopeptides, can literally fly on reverse phase.

But these alternative stationary phases have some drawbacks:

• They are not the standard method, and many times you won’t find TLC plates of alumina or reverse phase around in the lab.
• Correlating with being less available: they are more expensive than silica gel.
• In general, separation and resolution are worse. Also visualization can be more difficult in certain plates.

But sometimes (although very few times, we have to say) they are the only way to go, so keep in mind that these alternatives exist!

Finally, I have to mention that simple filter paper can be used as stationary phase. Separations are going to be bad, and you will get poor visualization. But if you have colored compounds, you can still see some separation. As a matter of fact, my first TLC experiment was just spotting a solution of spinach extract on filtering paper, and eluting it with acetone.

Visualizing Agents: Which One is Best?

There is no use in running a TLC if you cannot see the spots of the different compounds on your mixture. That’s why having access to the appropriate visualization technique is a must.

Visible or UV Light

Sometimes your compounds absorb visible light very strongly, and you don’t need visualizing agent at all. You can see the spots right as they elute up the plate!

This is common with highly conjugated compounds (such as polyaromatics, or polyenes), and with organometallic compounds, such as ferrocene derivatives. These compounds are great because you can basically run TLCs and column chromatography purifications knowing at all times where your compounds are on the silica!

However, most organic compounds do not absorb visible light strongly enough. So you have to use a visualizing agent.

The most common one is just using an ultraviolet lamp. TLC stationary phases are prepared to make your compounds visible in certain UV wavelengths. Most organic compounds, which have a minimum of conjugation will be observable in this manner.

But there are some compounds which don’t even absorb light on the wavelengths typically used in TLC UV lamps. Those are generally highly aliphatic compounds with little functional groups.

For these cases, we use staining agents.

Staining Solutions

Staining agents for TLC are basically solutions of one or more compounds in which we can dip the plates after elution. They will react with your products and help visualizing easily all the different spots/compounds present.

It is worth keeping in mind that, even if your target compound(s) absorbs strongly UV (or even visible) light, it is recommended to stain the plate anyway, if you can. This is because there might be other components of the mixture present as impurities which you cannot observe correctly under typical UV-Vis conditions.

So remember, even if your compound is visible at first sight, check also under UV light. And even if you can see everything under UV light, developing the plate with a general-purpose staining agent will almost never be overkill.

Now follows a list of the most typical staining agents, and how to prepare them. There are many others, some incredibly specific for certain types of compounds. But for the reasons, above, I’d always go with a general-purpose stain. And one of these will work for >95% of organic compounds, so pick your favorite, and go!

Acidic Vanillin

Many people use this vanillin solutions. It is really easy to prepare, and after heating, it is really sensitive to most functional groups.

The coolest thing is that many times, small changes in functionalities on organic compounds lead to a change in the color of the TLC plate after vanillin staining and heating. This is really great if your starting material and product have a very close Rf. You can still differentiate them by the color!

Specifically, it shows brightly most compounds with polar functional groups. It might not be great for highly apolar compounds, such as simple alkenes or aromatics.

The recipe for this stain is really easy: Weigh 10-15 g of vanillin, dissolve it 250 mL of ethanol, and add 2.5 mL of concentrated sulfuric acid. Stir and you are good to go! To use it just dip your eluted TLC plate, and heat up with a heating gun.

Phosphomolybdic Acid (PMA)

This is another great general purpose stain. It is my personal favorite, and it does color almost anything you can find in an organic chemistry lab. From polyaromatics to alcohols, going through alkenes, or simpler aliphatic compounds.

It gives you different blue-green shades, so it might not be the best for identifying different compounds with similar Rf, but for first choice, it will do great.

This staining solution is also extremely easy to prepare. You just need to dissolve around 5 g of phosphomolybdic acid (buy the lesser quality one for this purpose!) for each 500 mL of ethanol, and it’s done!

Potassium Permanganate (Basic KMnO4)

This is the most classical one, probably the cheaper option, and it is also quite general. Basically it turns your TLC plate purple, and every compound that can potentially be oxidized will show up as a yellow spot. This guy makes no distinction, and TLCs don’t look very pretty, but sometimes it does the trick.

The usual recipe is a bit more complex here, but nothing that you won’t find around in any lab. You basically need to dissolve 1.5 g of potassium permanganate and 10 g of potassium carbonate in 200 mL of water. To this mixture, add in 1 mL of 10% aqueous NaOH, and stir. Just be careful not to stain yourself with the mixture! You don’t want your skin to get oxidized (i.e. dark brown for a couple of days-weeks…)!

Cerium Ammonium Molybdate/Sulfate/Nitrate (CAM/CAS/CAN…)

This stain is also known as Hanessian’s Stain, or simply “blue stain” (for obvious reasons), and it is another multi-purpose beast.

It is a water based stain which makes your spots turn blue over a cool pale yellow background, after heating. If you heat too much, the background will also turn blue and the plate won’t look so nice, so be careful!

I have seen people use two different recipes. Both work more or less the same, it just depends in which cerium reagent you find around/is cheaper for you.

Dissolve 5 g of ammonium molybdate and 1 g of cerium sulfate (OR 2 g of cerium ammonium sulfate) into 100 mL of water. To this mixture, add 10 mL of concentrated sulfuric acid, and stir!

Other Staining Agents

There are many other staining agents, but they are usually more specific for certain types of compounds, and not the best ones to prepare or use routinely in the lab.

• Iodine vapor chamber: Fill a more or less sealed jar with a small spoon of iodine crystals. Cover it with silica gel. Put the dry eluted TLC plate in this developing chamber, and wait for the brown spots to appear. This is not the most sensitive stain, but the good thing is that you can use the same plate and develop it right after with a different stain.
• Ninhydrin: A solution of 10 g of ninhydrin in 250 mL of EtOH. It is great for amines, especially primary ones. Those will show up as green spots even before heating.
• Dinitrophenylhydrazine (DNP): Dissolve 1 g of DNP in 250 mL of aqueous HCl 2 M. This stain is extremely selective for aldehydes and ketones. Those spots will turn orange immediately at room temperature.
• Anisaldehyde: Dissolve 4 mL of anisaldehyde in 200 mL of EtOH. Then, add 3 mL of glacial acetic acid and finally 10 mL of concentrated sulfuric acid. The result is a stain very similar to vanillin. Maybe less selective and less easy to prepare, but sometimes, it makes for a wider variety of colors after development, allowing to distinguish very close spots on the plate.

Solvent Polarity: Reference Guide

To anyone with a couple of years of experience in the lab, choosing the solvent combination for running a TLC or a column comes really easy. Or at least a good starting point.

But for beginners, it can be really overwhelming. After all, there are a lot of different functional groups, and A LOT of different combinations. Not to mention the endless solvent combinations that you could imagine.

That is the reason why it is extremely difficult to find a good guide out there to choosing the eluent for chromatography.

A Solvent Polarity Guide for Thin Layer Chromatography

We wanted to get as close as possible to the best guide. And we came up with the following infographic for choosing solvents for TLC.

Keep in mind that of course this is an orientation and approximation, and there will always be compounds that behave weirdly. But we think that it will do the trick to for most situations, at least as a first shoot for a new reaction that you are running.

As you can see, we have broken down organic compounds depending on their functional groups, and added a value in the form of a % of polar solvent that you would need to your eluent mixture in order to get the compound with that group to go up the plate significantly.

We have limited it to classical mixtures of apolar solvent (hexane, pentane or cyclohexane) and polar solvent (ethyl acetate or diethyl ether), as a combination of these solvents will be usually enough to deal with most organic compounds.

Again, this is an approximation, and the values are not always additive. For example, an alcohol elutes with a 7:3 hexane/EtOAc. But if you have 3 alcohols, it is not certain that 1:9 will work. Maybe 1:1 is enough. Or maybe not even 1:9, maybe you even need to add methanol. There is no universal rule, that’s why guides such as this one are not very abundant.

As you can imagine, the most polar group itself will often dictate the polarity of the entire molecule.

Relative polarities of “minor” groups are important. Take a molecule which has an amide (6:4 hexane/EtOAc), but also a methoxy group (2-3% extra polarity). Then you change that methoxy group for an alcohol. Alcohol adds an extra 30-35% of polar solvent, so your reaction product spot will appear below the one for your starting substrate!

Which One of the Most Common Solvents is Better?

For practical purposes, solvents such as pentane, hexane, heptane or cyclohexane are similar, polarity-wise.

However, there are several considerations that might make you go for one or another.

Hexane/EtOAc is usually the standard mixture for organic separations. However, hexane is known to be a neurotoxic compound, that’s why many people swap from hexane to cyclohexane or heptane.

The only problem with those two solvents is that are less volatile, and more difficult to get rid of. If you need a more volatile alternative, use pentane. This should be used in cases where your target compound is relatively volatile and you cannot put it under high vacuum to remove the solvent completely.

In the polar component side, ethyl acetate and diethyl ether can be the main options. Diethyl ether is more volatile, so it should generally be avoided if possible, unless it gives you a much better separation or your target product is also volatile.

Also, when pairing solvent mixtures, try to go for solvents with similar volatility, so you don’t get faster evaporation of one of the components of the mixture than the other. This can potentially lead to reproducibility issues.

“Sticky” Compounds with Acid or Basic Sites

As an exception, you might want to consider as additives (up to 5-10%) of your mixtures other solvents such as MeOH (for extremely polar compounds), triethylamine (for compounds with basic sites) and acetic acid (for compounds with acid sites).

Compounds with basic or acidic sites, such as amines, amides (basic) or carboxylic acids (acid), can sometimes stick to the silica gel of the stationary phase a little bit too much.

This results on very wide spots on TLC, and as a consequence, very broad bands in your flash column chromatography purifications. Band/spot broadening often complicates purification, since your target compound might overlap with a byproduct or impurity that you want to get rid of.

Many times this has a simple solution: add to your solvent mixture 2-5% of triethylamine for basic compounds. This deactivates de acidic sites of the silica: Si–O–H bonds. These bonds, or extra protons, are responsible of basic compounds sticking to the silica gel, and making broader bands/spots. By adding Et3N to your eluent, you remove all of them and your compound will elute freely!

Similarly, acidic compounds such as carboxylic acids can react with Si–O bonds in silica gel to give Si–O–H, which really makes them stick to the stationary phase. You just need to add acetic acid as an additive, saturating Si–O sites into Si–O–H. This will make acidic compounds much more mobile through the TLC plate or column.

Preparative TLC

We have already covered flash column chromatography in a previous section. Running purifications is one of the main applications of thin layer chromatography.

But we can actually apply TLC to run preparative-scale purification. Not just to check how the different compounds/spots on a mixture separate, but to separate our reaction mixtures themselves, and isolate miligrams of pure products!

How Does Prep TLC Work?

Well, preparative TLC is just a regular thin layer chromatography separation, but with a bigger plate!

There are commercial TLC plates made specifically for prep TLC. They are usually made of glass coated with a thicker layer of silica gel. Then, instead of a single point spot, you apply the solution of your mixture (in roughly 0.5-1 mL of a volatile solvent such as DCM) along a line, parallel to the bottom (around 3-4 cm above the bottom).

For applying this solution, I usually use a 1 mL syringe with the thinest needle I can find. It has to be uniform and you need to be careful not to scrap the silica!

After drying it, you elute the plate in the appropriate solvent system (carefully chosen by classical TLC), and the different compounds will get separated. You obviously will need a bigger chamber. Typical prep TLC plates are around 30×30 cm.

Afterwards, you just need to scrap off separately the bands that you are interested in. For this, visualize the plate under UV light, and mark with a pencil the bands you are interested in.

Then, scrap off the band, and just pass a polar solvent such as DCM through the silica gel with your product, so it gets dissolved. Filter it off to get rid of the SiO2.

Then, just remove the solvent and there you go, pure product!

Preparative Thin Layer Chromatography: When Should I Use It?

So what are the advantages of preparative TLC?

• Allows you to separate compounds that are extremely similar in polarity. Often times, you can separate a little bit two compounds by TLC but they wont come separately after column chromatography. This is the perfect scenario to run prep TLC!
• You elute the plate several times with lower polarity solvent. If you need to perform a very careful separation, just use an eluent in which your compounds have a retention factor of around 0.10. Then, dry the plate, and elute it again. Repeat this process until your bands are well resolved.
• It’s handier than column chromatography. You just spot your compound, put the plate in the elution chamber and wait until the solvent goes up. Then dry and repeat until the level of separation pleases you. In the meantime, you can do anything else!
• It’s great to separate compound when you have only a few miligrams. Doing flash column of 10 mg of target product can be painful. This is not a problem with prep TLC.
• Sometimes you can use the same 30×30 to elute several mixtures. You can cut the glass plate on half to use different eluents, or just mark it in half with a pencil and deposit each solution in each of the halves, along the same parallel line.

But of course, there are drawbacks:

• It is not really scalable. I have separated up to 100-150 mg of compound using 2000 microns silica gel prep plates. But you cannot really go further than that in a practical manner. Preparative TLC is great for purifying the products of a reaction scope, or for the final steps of your total synthesis, but you cannot get grams of pure material with it.
• If your compound does not absorb UV or visible light, you will have a hard time knowing where it is on the plate. You can always “paint” a vertical line with a staining agent on one edge, and then heat. But I would only use this as a last resort measure.
• It is more expensive than flash column chromatography. No more to add to this, regular silica gel will always be cheaper than a commercial prep TLC plate. And making them yourself is really time consuming.

All this being said, I will leave you with a short time-lapse video of how does running preparative thin layer chromatography go:

Reporting Thin Layer Chromatography Data

TLC is a simple yet widely used technique. So in most reports and journals, you should provide information about TLC data for experimental procedures.

The very minimum is stating in which solvent mixture you have run the purification of each compound.

The best way, is reporting retention factors (Rf) of your product in a certain solvent mixture.

For example, you report a procedure to make benzaldehyde. You should mention that the product was purified by X chromatographic technique, using pentane/diethyl ether 1:1 as eluent, in which the product has a Rf of 0.75.

Tips and Tricks for Thin Layer Chromatography

We will finish by gathering some tricks, tips and lab hacks for TLC. You will definitely find something useful here!

2D TLC: Checking Compound Stability

Two-dimensional thin layer chromatography or 2D TLC got me through my first year of grad school, when I had to work with a great deal of compounds that could potentially decompose during purification on silica gel.

How to run a two-dimensional TLC

1. Get a square TLC: Cut a TLC plate with the shape of a square, around 7×7 cm is fine.
2. Spot the sample in one corner: Spot the solution of your sample in one of the corners of the square, leaving around 0.5-1 cm from each of the two borders.
3. Elute the plate in one direction: Use an eluent that gives roughly an Rf of 0.5 for your compound, and elute the plate as usual in one direction.
4. Elute the plate in another direction: Dry your plate, and rotate it 90 degrees, so the lane of all the spots is at the bottom. Elute it again on this direction.
5. Analyze the results: Any compound that is stable in silica gel, will appear somewhere in the diagonal of the square plate. Any compound that appears below the diagonal is decomposing.

Sand Bed for Your Elution Chamber

We have covered this sand bed for TLC in our lab hacks post.

If you have trouble leaving your plates standing vertically on your elution chamber, of if you want to run many plates on the same eluent at the same time… Get a big enough chamber, and make a bed with sea sand at the bottom (about 2 cm is enough)

Then, put your eluent in the chamber covering just a bit above the sea sand, and stick all the TLCs you need on the sand! They will not fall, and you can elute many of them parallel to each other.

Frequently Asked Questions (FAQ)

Closing Up and Conclusions

We really hope this comprehensive guide can help you master this wonderful technique.

Also, thanks to Lisa Nichols for borrowing some of her images from: Organic Chemistry Laboratory Techniques, Nichols, 2017.

Top sum up, o matter if you are new to synthetic chemistry or an experienced researcher, we hope you have learnt something from it!

Also we would love to hear from you and read your feedback and questions!

So please, head right into the comment section, and ask whatever you want. Remember that there are no stupid questions.

Any criticism and suggestion to improve the guide further will be highly appreciated. If you think that something is missing, or not well explained, go for it.

Finally, if you found this guide useful, please, feel free to share this on your websites, with your students or colleagues, or anywhere you like.

The post Thin Layer Chromatography: A Complete Guide to TLC appeared first on Chemistry Hall.

We have reviewed and updated this guide recently, so it is ready for 2020. You can check the best available options right now.

Get ready to share a great adventure into chemistry together with your kids!

Why Do Chemistry Experiments at Home?

Kids are naturally curious about the world around them. Satisfying and encouraging that curiosity will help lay the foundation for a lifelong love of learning.

Chemistry is driving practically everything that happens in the universe, and the best way to learn it is to see it in action. Think back to your own schooldays. What parts of science class were the most memorable? The experiments and demonstrations!

Chemistry is an empirical or experimental science, and it is extremely difficult to make it enjoyable for a kid using only theory, or textbook explanation. Many chemists even admit to not like chemistry very much when they were kids! This was because their learning experience lacked of experiments.

Basically, the reason to find the best chemistry set for kids with age-appropriate experiments is that they are educational and totally cool. Students of all levels can learn important science concepts and have tons of fun doing it.

We have previously covered how to set up a home chemistry lab, but today we focus on another very important topic: learning together with our kids!

And this kind of sets go beyond learning chemistry. If you are interested in other fields of science, you should go and get your hands into a science kit.

If you are looking for something to give as a gift to a chemist, check out this gift review!

In this post, we’ve got our pick for the best chemistry set for kids, as well as detailed reviews for eight different chemistry kit products, all ideal for classroom or home use.

Our Top Choice for Best Overall Chemistry Kit

As always, we start this review post with our number one pick. Today, that designation goes to the Thames & Kosmos Chem C2000 kit. This would be considered the intermediate chemistry set, between the C1000 and the C3000 products.

Thames & Kosmos Chem C2000 (V 2.0)

We rate this best overall because of the amazing number of projects, quality materials and full-color experiment manual. It is on the higher end of the price range among the kits in this article, but with everything you get, it is a great value.

Chem C2000 was the best in 2019, and is still the best option out there in 2020.

The Chem C2000 chemistry set includes around 250 experiments with professional quality equipment. As such, it is ideal for homeschooling and traditional classrooms alike.

Thames & Kosmos recommend this kit for ages 11 and up; after all, there are some pretty serious chemicals in here, not to mention an alcohol burner for experiments that require heat.

Quick Comparison Table

The Best Chemistry Sets for Kids

Now, starting with our top pick, we’ve got detailed reviews of eight products which provide fun chemistry experiments for kids of all ages.

1. Thames & Kosmos Chem C2000

Thames & Kosmos offer a range of Chem kids’ science kits, and the C2000 falls right in the middle in terms of extensiveness, level, and price. It comes with the equipment and supplies you need for some 250 experiments with a comprehensive lab manual to guide budding scientists through each activity.

Thames & Kosmos Chem C2000

We would rate this as the ideal beginner chemistry set for older elementary school and up. Thames & Kosmos are famous for their award-winning products, so it’s no wonder they rolled out the best science kit for kids. Both this and the more basic C1000 kit have won awards from the Parents’ Choice Foundation.

Although it does not have as many experiments as the C3000 kit, it is very complete and very professional. It is recommended for ages 11 and up, but honestly, adults are just as likely to find this chemistry kit enjoyable and educational as children are.

Of particular note in the C2000 set is the alcohol burner, which greatly expands the number of possible experiments by providing a heat source.

2. Thames & Kosmos Chem C3000

This product is, of course, the more advanced premium option from Thames & Kosmos. Compared to the C2000 model, this chemistry kit has about 333 experiments, with extremely high quality equipment.

Thames & Kosmos Chem C3000

If you don’t mind the higher price point, this would definitely be the best chemistry set for adults of all the products on this list. It is just about the closest thing you’ll find to a professional chemistry set out there.

The C3000 model is recommended for ages 12 and up, and its experiments cover some fairly advanced topics. It would make a great companion to high school science, and would be right at home in the classroom as well.

If you are looking for a more advanced chemistry set for teenagers, this is probably a very nice bet.

3. Thames & Kosmos Chem C1000

Once again, another product from Thames & Kosmos that ranks among the best science kits for kids. Unlike its higher-end counterparts, the C1000 has just 125 experiments. However, this is still a very complete set, recommended for ages 10 and up.

Thames & Kosmos Chem C1000

Perhaps the most obvious benefit of the C1000 chemistry set compared to the other to is its more affordable price. Considering everything you get, we would still call the C2000 a better overall value, but this is another excellent choice.

Also, the Parents’ Choice Foundation has dubbed this one of the best chemistry sets for kids, too, by giving it their gold award.

4. Ben Franklin Toys Chemistry Lab Pad Science Kit

This product from Ben Franklin Toys is one of several options for chemistry kits for kids in preschool and early elementary school. Accordingly, it puts a focus on safety and exploration, and it is designed for children ages 5 and older.

Ben Franklin Toys Chemistry Lab Pad Science Kit

The distinguishing feature of the Lab Pad Science Kit is, you guessed it, the lab pad. Parents and preschool teachers will appreciate the lab pad, because it serves as both a work surface for experiments and storage for all the included equipment. As a result, everything stays nice and organized in between science days.

However, the experiments in this product are very limited. In contrast to the other chemistry sets on this list—even the ones designed for younger kids—it only has around 12 activities to do. The price for this product is in the middle of the range, but if you are looking for a great variety of experiments to do with your kids, then it might not be the best value.

5. Learn & Climb Kids Science Kit

Another chemistry set for kids designed for the preschool and kindergarten age group, the Learn & Climb Fun with Science kit is suitable for ages 5 and up.

Learn & Climb Kids Science Kit

Unlike the previous product, Learn & Climb provides a much more complete kit. It contains over 60 experiments, compared to just 12 in the Ben Franklin Toys product, and it retails for a lower price.

In fact, we would rate this as the best chemistry set for kids between the ages of 5 and 10. The number and variety of activities is quite impressive, it is very affordable, and it is designed to help kids learn and explore independently. On this last point, the kit includes a kid-friendly experiment manual and an instructional DVD to guide young scientists through each project.

6. Learning Resources Primary Science Deluxe Lab Set

If the Learn & Climb science kit is the best option for elementary school-aged children, then this lab set from Learning Resources is the best chemistry set for kids who are still in preschool. Designed for children as young as 3 years old, it is perfect for the youngest scientists.

Learning Resources Primary Science Deluxe Lab Set

This kit comes with 20 double-sided activity cards that guide students through experiments with step by step instructions. Altogether, it’s a great kit for giving kids their first exposure to real scientific equipment, like test tubes, flasks, funnels, and even a “science view scope” that looks like a microscope.

So, if you want to encourage scientific exploration in your children or students between the ages of 3 and 5, then this would be our top recommendation.

7. Dan & Darci Light Up Crystal Growing Kit

One of the most rewarding and visually impressive science experiments you can do with your kids is crystal growing. While natural crystals take thousands of years to form in the ground, crystal growing kits like this one from Dan & Darci take just one week or less to form beautiful crystals that will fascinate children and adults alike.

Light-up Crystal Growing Kit for Kids

Although the kit is not recommended for use by kids under 8 years old, your younger kids can still get excited checking the crystals each day to see how much they’ve grown.

The Dan & Darci crystal growing kit is very reasonably priced for this type of product. It comes with materials to grow three crystals: one red, one blue, and one colorless. All you have to do is add boiling water and follow the instructions.

Arguably the most standout feature of this specific crystal growing kit is the LED light display. Once your crystals have finished growing, simply use the included USB charging cable to charge the LED display, and then set your crystals on top and enjoy the beautiful results.

8. Happy Atoms Magnetic Molecular Modeling Complete Set

When kids start learning about atoms and molecules in middle and high school, the new information can be very abstract and overwhelming. Don’t let this discourage them! Instead, help them feel curious and confident by putting those molecules right in their hands.

Happy Atoms Magnetic Molecular Modeling Complete Set

This Happy Atoms kit might seem somewhat expensive for a molecular modeling kit; however, it has a very innovative special feature that accounts for the more premium price. In addition to the magnetic atoms and bonds, it comes with a scanning mat and a free app download that will scan and identify the molecules your child builds.

Because of this, it is a great tool for kids aged 10-17 as they go through their first dedicated chemistry classes. Also, it comes with 216 enrichment activities that are fun and sure to foster a love of science.

If you want more info on molecular modeling kits, make sure to check our previous review.

FAQ (Frequently Asked Questions)

In all cases, any time you are performing chemistry experiments, always make sure that you wear lab safety glasses. Protect your eyes (and your kid’s) at all costs.

Choosing the Best Chemistry Set for Kids

Luckily, this is a very easy choice for parents and teachers to make. After all, the main factor to consider is the age of the children who will be using the kit.

If your young scientist is at least 10 years old, then one of the Thames & Kosmos chemistry sets will be most appropriate for general chemistry experiments, especially the Thames & Kosmos Chem C2000 model. This is a great option that even adults will enjoy. The chemistry kits from this series are a great complement for learning chemistry in high school too.

If they are taking chemistry in high school, teenagers would also strongly benefit from the Happy Atoms molecular modeling kit and its companion mobile app.

For elementary-aged kids, approximately ages 5-10, we would recommend the Learn & Climb Kids Science Kit. This is because of its excellent array of experiments compared to similar products, its great value, and its clear focus on kids.

Finally, the Learning Resources Primary Science Deluxe Lab Set is certainly the best chemistry set for kids who are still in preschool and too young for the Learn & Climb kit. With visual instructions, bright colors, and safe experiments, it’s ideal for ages 3+.

If you want to check out some chemistry experiments that you can do at home without having to purchase any kit, make sure to check these examples.

So you see, there are great options available to do fun chemistry at home no matter where you kids are on their learning journey. These experiments are so cool, they won’t even realize they’re educational!

The post The Best Chemistry Set for Kids (and Adults!) appeared first on Chemistry Hall.

Whether you are a chemistry instructor at the university or high school level, or a student looking for some guidance, we’re here to help!

This guide for chemistry instructors and students will help you choose the best chemistry textbook for your particular course.

Choosing a Chemistry Textbook as an Instructor or Student

In this guide, we’ve put together detailed reviews of some of the best general chemistry text books and related resources, along with handy quick comparison tables to help you make the best decision. But first, a few tips for both instructors and students on picking the right book.

We have previously covered reviews for the best textbooks for organic chemistry and inorganic chemistry. It was about time that we reviewed also the best books for general chemistry! On the other hand, if you are looking for help to learn chemistry in high school, check some of these other books.

In a perfect world, instructors would consider the quality and relevance of the content and the needs of their student population.

Unfortunately, textbooks are often assigned to classes by department heads and not by the professors who actually teach the class.

When teachers and professors are given the freedom to choose their text, the most diligent will ask questions such as those posed by Dr. Robert Sherman of Miami University:

Does the book match our course content, and is the overall organization reasonable? Is the material at a level at which I plan to teach? Is the information accurate? Is it well-written, with good illustrations?

A dilemma emerges when it comes to the writing style of science textbooks. Students value clarity above all else, and lots of technical jargon can be an obstacle for them in understanding a text. However, instructors will sometimes view terminology-dense writing as being indicative of the author’s expertise in the field.

As for students, they will usually choose the chemistry textbook that appears on their professor’s syllabus, especially if it is listed as a required material for the class. However, they may want to choose another title if the instructor allows it or supplement the required textbook if it doesn’t adequately meet their needs.

Some books are written more clearly than others, and every student’s learning style is different; a visual learner may prefer a text with plenty of illustrations, while a hands-on learner might benefit from a book bundled with interactive content and practice problems. There’s a best tool to learn chemistry for everyone.

The Best Chemistry Textbook: Our Top Choice

With that out of the way, we can get straight to business and talk about our top choice for what is, in our opinion, the best general chemistry textbook that will suit the needs of most college professors and students. It would also be appropriate for an AP chemistry course in high school taken for college credit.

However, in this review guide, we actually have two top choices depending on the student’s budget. First, the more economical option, which is Brown et al.’s Chemistry: The Central Science. This textbook is in its 14^th edition, which speaks volumes for the quality of the material. Its biggest strengths are the student-friendly explanations of the most essential concepts for general chemistry 1 and 2 and, its helpful practice problems, and emphasis on practical applications.

The other candidate for best overall general chem book is Tro’s Chemistry: A Molecular Approach.

Although this is a more expensive option. Of all the textbooks in this review guide, this seems to be the most universally student-friendly one. It is especially ideal for visual learners and students who like to work through practice problems to master the material. The sample exercises are much more helpful than in an average chemistry textbook because they run the gamut from basic conceptual questions to more complex problems so that you’re prepared for anything.

Quick Comparison Chart of the Best Chemistry Textbooks

Before we get into the detailed reviews of each item on the list, here is a table with the most important information:

The Best General Chemistry Textbooks

Now for the meaty stuff: detailed chemistry textbook reviews to help you choose the best book for your students, if you are an instructor, or for personal use as a student. The first two items on the list are our top picks for economy and premium textbooks, respectively.

Chemistry: The Central Science

Brown et al.’s Chemistry: The Central Science is our top economy pick and an overall great textbook.

Chemistry: The Central Science

We rate this the best general chemistry book for students on a budget, but even if you aren’t strapped for cash, it is an excellent option. It has made it through 14 editions so far, and they wouldn’t keep printing new editions if it wasn’t top quality.

The book’s main strengths are:

• Core concepts are explained very clearly
• Shows practical applications for chemistry in everyday life
• Practice exercises help students understand the material and improve problem-solving skills
• One book will get you through both semesters of college or university general chemistry

The main drawback is that, while most chapters are engaging, easy to understand and explained very well, some parts are a bit dry, which may make it more difficult for students to grasp these specific concepts.

Chemistry: A Molecular Approach

We rate Chemistry: A Molecular Approach by Nivaldo J. Tro as the best chemistry textbook overall on our list and easily one of the best general chemistry books for undergraduates you can find.

Chemistry: A Molecular Approach

Just like the first title, this text contains all the relevant material with logical organization and clear explanations.

What makes Chemistry: A Molecular Approach stand out, though, is how obvious it is that everything was written and put together with students in mind. The many visual aids provided alongside the text excel at helping students understand tough concepts.

Another point in its favor are the high-quality practice exercises with scaling levels of difficulty to deepen students’ understanding of each concept and give them opportunities to apply that knowledge.

The main advantages of this book are:

• Written with students in mind
• Excellent visual aids
• Lots of sample problems with difficulty ranging from basic to cumulative
• Contains all the material you need for general chemistry 1 and 2

Apart from the more premium price point, the only negative thing we can say about this chemistry textbook is that the various topics are not always given equal weight or consideration. In some chapters, students may feel they are inundated with information, while other chapters may not provide a suitably in-depth explanation.

General Chemistry: Principles and Modern Applications

General Chemistry by Ralph H. Petrucci is a perfectly acceptable general chemistry textbook, and a little cheaper than the top two books in its hardcover edition. It is well written and logically organized, and it has everything you will need for gen chem 1 and 2.

General Chemistry: Principles and Modern Applications

There’s just one issue that has disappointed several customers on Amazon, and that is that the digital edition of the textbook for Kindle and e-reader has major formatting issues. The text itself is readable, but mathematical equations and formulae are sometimes nearly indecipherable.

Despite the very low price of the digital edition, we recommend you choose the print version instead to avoid frustrating formatting errors.

General Chemistry: The Essential Concepts

For anyone who just has a casual interest in the subject, Chang’s condensed book of essential concepts in chemistry might be the best chemistry textbook for self-study.

General Chemistry: The Essential Concepts

It is also a fine choice for students in a formal class, because it is designed to cover all the material taught in two semesters of general chemistry as concisely as possible, without weighing you down with topics your professors will never lecture on.

According to the editors, these qualities make the book 200 to 300 pages shorter than an average chemistry textbook, which, naturally, makes it a more affordable option as well.

Chemistry: An Introduction to General, Organic, and Biological Chemistry

This book by Karen C. Timberlake offers an introduction to three of the major fields of chemistry. Therefore, this book could be described as the only introductory chemistry text you’ll ever need.

Chemistry: An Introduction to General, Organic, and Biological Chemistry

Designed with allied health students in mind, it is the best chemistry textbook for college students who plan to take one-semester courses in these different chemistry disciplines.

It provides plenty of examples of real-life applications of chemistry, with a focus on health care and environmental science.

Introductory Chemistry Essentials

This introductory chemistry book is written by the same author as our top pick (Nivaldo J. Tro), which gives you a clue as to its level of quality.

Introductory Chemistry Essentials

It is truly an excellent textbook for preparatory or introductory chemistry courses, but not in-depth enough for two semesters of gen chem.

With its clear explanations that make tough concepts easy for students to understand, we would rate this as the best chemistry textbook for high school of all the titles included in this guide. It may also be appropriate for remedial or introductory chemistry courses at the college level.

All in all, a high-quality text that is easy to use and ideal for students who are new to chemistry.

Chemistry for Dummies

As you can guess from the name, this is not a textbook, but it can be an extremely helpful supplemental resource for a better understanding of core concepts.

Chemistry for Dummies

It can be used at practically every level of basic chemistry, from undergraduate general chemistry to high school chemistry and even middle school science. Chemistry for Dummies covers all the essential concepts and skills you need to succeed in chemistry, but in language that is simpler and more straightforward than most textbooks.

Chapter topics include: chemical calculations and units, matter and energy, atomic structure, the periodic table, gases, chemical reactions, the mole, solutions, thermochemistry, acids and bases, quantum theory, ionic bonding, covalent bonding, molecular geometry, periodic trends, intermolecular forces, environmental and nuclear chemistry, and other fun sections such as “Ten (Or So) Great Chemistry Nerds” and “Ten Terrific Tips for Passing Chem I”.

Summary of Our Best Chemistry Textbook Guide

So, there you have it! Our roundup of the best chemistry books includes several general chemistry texts, a more expansive allied health text, and a great study aid, all of which cater to just about every level.

The first two spots on this list correspond to our top two picks. If you have the option to choose your own textbook or want a supplemental resource because you don’t like the one your professor assigned, either of these would be perfect. Our choice for best overall, Tro’s Chemistry: A Molecular Approach, falls at the higher end of the price range—it’s what you would expect to pay for a new, hardcover college textbook these days.

A more budget friendly option is Brown’s Chemistry: The Central Science. This is another excellent textbook, but a quick note on editions: the “Global Edition” is priced significantly below the standard “A La Carte Edition”. Most American colleges and universities recommending this textbook will be referring to the a la carte edition, and this may be what your professor is expecting if they consider the book a required material.

However, students who have used the global edition in their classes say that the chapters themselves are essentially the same as in the a la carte edition, but the end of chapter questions are different. So, you can save money by choosing the global edition, just keep in mind that if your teacher asks for those questions to be worked out as part of an assignment, you might not have direct access to them.

Further Options for the Best Chemistry Textbook

With those two clear winners, assigning third place is a bit more complicated because of the different focus each of the remaining books has. For a traditional general chemistry book, that spot would go to #3 on the list, Petrucci’s General Chemistry: Principles and Modern Applications because it is most likely to meet the needs of most gen chem students as a main course textbook.

However, if you already have your professor’s required textbook but aren’t happy with it, and you don’t have a ton of cash to spend on an additional book this semester, Chang & Goldsby’s General Chemistry: The Essential Concepts would be a perfect supplement without weighing you down with drawn-out explanations or extraneous information.

Every chemistry professor has different expectations and teaching style, just like every student has a different learning style.

Use the reviews in this guide to help find the chemistry textbook that fits your needs best.

And remember to get a cool chemistry gift to your teacher!

Whichever you choose, you’ll be one step closer to understanding how chemistry affects every aspect of our lives!

The post The Best General Chemistry Textbook appeared first on Chemistry Hall.

We have recently reviewed a selection of the best organic chemistry textbooks. Shortly after, we started to receive emails asking for similar recommendations, but directed towards inorganic chemistry. There’s a slight big difference between organic and inorganic chemistry, so different approaches are often employed to teach learn each one of the two.

So we decided to go back to the library a check the best texts for this fascinating and diverse subject. This resulted on a nice and concise review guide of 6 books which we believe are the best for learning inorganic chem.

This reference guide is aimed at education professionals that are looking for a textbook to base their inorganic chemistry syllabus on. But also to all inorganic chem students that do not have a defined textbook on their courses, or want a better one to fully understand the topics on their class.

As always, we start off by cutting right to the chase and present what we believe is the best inorganic chemistry textbook, overall.

What Is the Best Inorganic Chemistry Textbook?

From our point of view, Inorganic Chemistry by C. Housecroft and A. Sharpe is the most recommended textbook for inorganic chemistry. It approaches many areas of this wide subject in a very methodical and logical fashion.

Housecroft Inorganic Chemistry

It is the best book we have put our hands into so far.

This text is very detailed, even in the more specialized chapters. If you buy it, it will probably be the only introductory textbook that you will ever need for any inorganic chemistry university course.

Quick Summary Table of the Best Inorganic Chemistry Textbooks

Here we have condensed the six reviews included on this guide in a reference table. You can take a quick glance at the best features of each option, or continue reading for the complete reviews!

1. Housecroft Inorganic Chemistry

Our number one choice is Inorganic Chemistry by Catherine Housecroft and Alan G. Sharpe. It is the text I used though my undergraduate courses years ago. And it is the first choice for many educators I know.

Housecroft Inorganic Chemistry

Housecroft is greatly organized, and the explanations are easy to understand. But this does not sacrifice level of detail. Most topics are explored deeply.

Many questions and problems are provided in order to help you grasp all the concepts on each chapter. The book has review sections which work greatly for this purpose.

This best inorganic chemistry textbook is filled with beautiful and attractive schemes, pictures and images. Most inorganic chemistry textbooks don’t really have illustrations as powerful and instructive as Housecroft’s.

This textbook is right now on its 5th edition, released in 2018, so its 1300 pages are full of updated content.

It is also worth highlighting how real-life or interdisciplinary applications of pure and basic inorganic chemistry concepts are described throughout the book.

Overall, in our opinion, Housecroft’s is the most complete inorganic chemistry textbook. It is wide, but also deep enough so you will be able to push through any introductory inorganic chemistry course with it.

2. Miessler Inorganic Chemistry

Inorganic chemistry by Miessler and Tarr is another pretty standard option. The last edition brings colored images and diagrams which make the textbook much easier to follow.

Miessler Inorganic Chemistry

This book is very accesible, and describes concepts very visually. It even goes into some computational chemistry. This is generally an advantage, but there is people that, for this reason, find some of the concepts difficult to grasp without a solid basic knowledge on physical chemistry.

For both professors and students, Miessler’s is one of the best options if you want teach or take medium to advanced inorganic chemistry courses. It finds interesctions between physical and organic chemistry, which is good.

As a drawback, it lacks a bit on the problems and exercises department. You will need the corresponding solutions manual, which fortunately is not that expensive. You can find it here.

3. Cotton-Wilkinson Advanced Inorganic Chemistry

Advanced Inorganic Chemistry is probably the best and most complete reference inorganic chem textbook out there.

We wouldn’t choose it as the best option for basing an introductory inorganic chemistry course on, but it is difficult to beat for anything above that. It is a classic masterpiece, written by F. Albert Cotton and the Nobel laureate Sir Geoffrey Wilkinson.

Cotton-Wilkinson Advanced Inorganic Chemistry

If you are either a professional or somebody looking forward to develop a career on inorganic or organometallic chemistry, this textbook should be in your shelf. On the other hand, if you are a student which enjoys inorganic chemistry a lot, and you already have covered the basics of chemistry in class, this book might be your perfect choice. If you want something for self-study or reference, or as a suplement, Advanced Inorganic Chemistry by Cotton and Wilkinson will do the job.

I’m actually an organic chemist and this reference book has been right next to me on my room for a lot of years. It is a great text for both inorganic and organometallic chemistry students (or professionals) alike.

In contrast with other typical textbooks, Cotton-Wilkinson’s Advanced Inorganic Chemistry is organized by elements, describing all the typical compounds for each element, going through bonding and reactivity. This arrangement makes it the absolute best book for just picking it up and starting to get into the inorganic chemistry of one element you are particularly interested in. It has plenty of relevant references to go through and expand your knowledge.

Some describe this book as more like a dictionary or reference guide than a textbook, that’s why using it for introductory courses might not be the best choice. But for reference and self-study, it is the best inorganic chemistry book out there.

4. Weller Inorganic Chemistry (Former Atkins)

Over the years, one of the golden reference textbooks was Inorganic Chemistry by Shriver, Atkins and co-workers. Atkins is no longer updating his book, but his co-workers, Mark Weller, Tina Overton and Jonathan Rourke, took over with this Inorganic Chemistry textbook.

This is the last edition of one of the best inorganic chemistry texbooks out there. Together with Housecroft’s, make up probably the top 2 best textbooks for introductory inorganic chemistry courses.

Weller Inorganic Chemistry

This inorganic chemistry textbook goes generally into more detail than Housecroft’s, but it is generally not as easy to read, especially if you are just getting started.

For chapters such as the ones for the crystal/ligand field theory (the base for coordination chemistry), it is great and very detailed. If you are approaching organometallic chemistry, this text may be the way to go. Another advantage is that it seems to be cheaper than the original Atkins used to be. Also, it was updated in 2018.

Overall, if you want something that goes into a bit more of detail than Housecroft (although covering a less broad amount of material, and with less examples), or if for some reason you don’t like that text, Weller’s Inorganic Chemistry is probably your best bet.

5. Lee Concise Inorganic Chemistry

As you can probably tell from its name, Lee’s Concise Inorganic Chemistry is a textbook that goes right to the point. It does not contain things that the author may consider to be not relevant. This can be good, but it also means that you might find that it lacks examples in some cases.

Lee Concise Inorganic Chemistry

It may be a “concise” textbook, but by no means it is short in content. Throughout its 1000 pages, Concise Inorganic Chemistry is one of the best introductions to the subject there is. I’ve known people that have used it from preparing AP chemistry exams, or SAT chemistry subject tests, to getting through university courses.

As most inorganic chemistry texts, it starts describing the different bonds and trends on the elements of the preiodic table. Then it quickly jumps into describing groups of elements. You won’t find many discussions such as “why is this element important” or “what are the every day uses of this kind of compounds”, instead, Lee focuses on properties, structure and bonding.

However, don’t think that this book would be too boring because of this. It is actually one of the most enjoyable inorganic chemistry textbooks to read. There is a great balance between theory and applications. And it is definitely one of the best choices if you just want to prepare for an inorganic chemistry course.

6. Chemistry: A Molecular Approach

First of all, Chemistry: A Molecular Approach is a general chemistry textbook, not an inorganic chemistry one.

So what’s it doing on this review?

Well, in contrast to the other areas of chemistry (which usually need a more specialized text, even at introductory levels), the content of introductory inorganic chemistry courses usually overlaps with what you can find in most general chemistry textbooks.

This is because most introductions to inorganic chemistry are strongly based and centered around the different concepts of chemical bonding. And this is amazingly well explained in general chemistry textbooks. Specifically, Chemistry: A Molecular Approach by Nivaldo J. Tro does an excellent job on this sense.

Chemistry: A Molecular Approach

If you are just getting into inorganic chemistry, you can perfectly stick to this textbook.

It covers, from the very beginning, all basic concepts of chemical bonding. From the Lewis model to a latter chapter on transition metals and coordination compounds.

However, it is a general chemistry text, after all. If you move deeper into any field within inorganic chemistry, you will probably run out of content pretty soon.

If you want more information about general chemistry textbooks, check out our review post to look for the best one for you!

Overall, this a perfect choice if you are just getting started with inorganic chemistry, and you want a book that can be versatile: you will be able to use it in many other introductory chemistry courses! You need a base to study any field of chemistry. Chemistry: A Molecular Approach does a great job on providing this base, particularly for inorganic chemistry.

Final Thoughts and Summary

To sum up, if you are in doubt, go for Housecroft Inorganic Chemistry. Overall, it is the best option. It will fit any inorganic chemistry course that you want to teach or take.

If you are going to take or teach an advanced inorganic chemistry course, or you want a book that can serve as reference for future courses, or in your chemistry career, go for Advanced Organic Chemistry by Cotton and Wilkinson.

Finally, if you are just taking basic inorganic chemistry courses, and you are just getting started in chemistry, a general chemistry text will be the best fit. It will also be useful for introductory courses on other branches of chemistry. Our best recommendation for this case is Chemistry: A Molecular Approach.

You can take a quick glance or purchase the best option for your needs through the following table:

If you want further information or educational resources, make sure to check our guide to learn chemistry.

Enjoy learning inorganic chemistry!

The post The Best Inorganic Chemistry Textbooks appeared first on Chemistry Hall.

The so called central science offers us so many awesome things to think about. From chemistry facts in daily life to recent scientific discoveries. Therefore, it is not an easy task to put together an objective list of the most interesting questions and facts that you can find out there.

But we did a great deal of research to finally come up with a massive list of facts about chemistry and explanations. It has been cooking slowly for weeks, but it is finally here!

We did our best to collect no less than 100 of the most popular fun chemistry facts!

We consulted chemistry forums, and typical questions that people ask on search engines. Of course, we also used our own personal experience on what kind of chemistry questions we keep getting asked as chemists.

This is a long list of chemistry facts, so feel free to use the table of contents to navigate through it. Start reading about whatever catches you attention, and come back later to the list!

If something strikes you as an interesting fact about chemistry, we have succeeded in our mission!

We like a lot the result, and we want this to serve as a scientific outreach resource, so if you like it too, make sure to link or share this website among your students, friends, colleagues or any potential chemistry enthusiast!

By the wat, if you are interested in learning more fun chemistry with your kids, get your hands into one chemistry set now, and start enjoying the best part of chemistry: experiments!

Table of Contents

You can use the next table of contents to navigate directly to the question you are interested on the most:

What Kind of Chemistry Facts Are We Going to Learn About in This Article?

This research resulted on a selection of one hundred interesting and fun chemistry facts that can be explained and enjoyed by most audiences (don’t worry, you don’t need a PhD in chemistry to understand the explanations!).

We present them in the form of questions and also try to explain them in the more concise, and clear way as possible, for a broad audience, but without compromising scientific rigor.

We also cite reliable sources so you can expand further in all the covered topics. This list is obviously not meant to offer deep or exhaustive explanations, just the tip of the iceberg. Enough to light up you attention towards any interesting chemistry fact or story.

You will find also many facts that can be even interesting for young students or kids. If you are taking care of those, maybe you want to add some more fun to their scientific education and play with a chemistry set with them!

We have previously looked into some essential basic chemistry concepts, we suggest you to take a look at them if you are not very familiar with chemistry. Furthermore, if you are an early chemistry student, maybe you want some help to prepare for your ap chem exam. But for now let’s just get into some really interesting and fun chemistry facts.

Without further ado, let’s dive into answering the best chemistry questions that we could come up with!

We hope you enjoy the chemistry and we guarantee that you will learn something cool out of it!

1. How Do Glow Sticks Glow?

A glow stick is a self-contained light source. It is basically a plastic tube, in which different substances are contained: mainly a basic catalyst and a dye. Inside the plastic tube, there is a glass vial is filled with the other required component: hydrogen peroxide (H₂O₂).

When the glass vial within the plastic stick tube is broken by the user, all the components are mixed together. Then, a series of chemical reactions take place. This results in the excitation of the “dye” molecule, which upon relaxation releases light through a process known as chemiluminescence.

Hydrogen peroxide reacts with diphenyl oxalate giving peroxyacid ester. This molecule decomposes spontaneously, giving CO₂ and releasing energy that can excite the dye molecules. The excited dye molecules can relax back, releasing photons of light of different colors. Depending on the nature of the dye, the color (wavelength) of the emitted light will be different.

For example, typical green glow sticks use 9,10-bis(2-phenylethynyl)anthracene as dye.

2. How Do You Make Fireworks of Different Colors?

Two thousand years ago, a cook mixed three ingredients very common in any kitchen: potassium nitrate (food preservative), sulphur and charcoal. Mixed and and heated, they go off exploding on a huge bang. This is basically gunpowder.

If this mixture is put on a cane, pressure builds up giving rise to a bigger explosion. Originally, potassium nitrate was used. Potassium cations are responsible of a white color. If different salts are used instead, with different metals as cations, you get the different colors. For example, strontium salts give red colors. Iron compounds give gold-colored fireworks. Also, sodium gives yellow, barium gives green and copper gives blue. There is a great infograhic by Compound Interest about this.

3. How Does Ozone Destroy Elastomers?

Ozone (O₃) is a strongly oxidizing agent, and it is reactive towards double bonds in a chemical process known as ozonolyisis.

This oxidative reaction which splits double bonds into two carbonyls, is the process that disrupts the rubber polymer in elastomers, such as wheel tires and rubber tubing. But you don’t need huge amounts of ozone to get the cracking initiated, only a very small amount of O₃ gets the process going.

4. Why Do We Add Fluorinated Groups to Many Drugs?

This goes beyond basic knowledge, but sometimes you see that medicinal chemists decide to “randomly” put a F atom in a molecule. This is a common pattern in drug design, which is weird because fluorine appears very rarely in naturally occurring molecules.

Fluorine is a element that is usually added to drug molecules because it can increase its selectivity. Also, adding fluorine atoms increase the solubility of the drug in fats, making it easier for it to go through body barriers. Furthermore, the simple exchange of a H atom by a F atom in a certain position, make it much more stable, and less prone to degradation by oxidation. This may have a significant positive effect in the dosage of the drug.

5. Which Are the Only Elements Liquid at Room Temperature?

The only pure elemental compounds (which are, compounds made of atoms of only one element) that are liquid at room temperature are Br₂ (fuming orange liquid), and mercury (a metal).

6. Where Did Most of the Oxygen in the Atmosphere Come From?

Surprisingly, 20% of the world’s oxygen is produced in the Amazon Rain forest. This is the largest rainforest on Earth. Its Basin covers 40% of the South American continent.

7. What is the Toughest Total Synthesis Ever Accomplished?

Arguably, this top spot must be given to the first total synthesis of cyanocobalamin, or vitamin B12. This vitamin is used, ironically, to treat vitamin B12 deficiency. Its first total synthesis was carried out between two huge research groups, the group of Robert B. Woodward (at Harvard University) and Albert Eschenmoser (at ETH Zurich). You can take a look at some online chemistry lectures by Woodward and other chemistry giants.

12 PhD students and 91 post-doctoral researchers were involved on this huge project, that took more than 12 years to go to completion. The total synthesis was completed in 95 steps. This step count is insanely difficult to deal with. Even if all the steps gave 90% yield, the overall yield would be (0.9^95)·100 = 0.0045%. But actually, several steps have yields lower than 20%, so the amount of starting materials required for accomplishing such task, would have been enormous. And all of this was carried out in a time in which characterization techniques such as spectroscopy were very limited to non-existent. If you are just getting into the wonders of organic chemistry, you should get your hands into one of the best textbooks out there! Also make sure to check out some organic chemistry model kits.

8. What Is Hot Spicy and Cold Spicy?

Peppers and similar “hot spicy” food are so due to a molecule called capsaicin. The heat of the spiciness is measured by the Scoville Scale. On the other hand, “colder” spicy condiments such as wasabi, but also mustard or horseradish, the molecule to blame is allyl isothiocyanate. The receptors for allyl isothianate can make your body sting, burn cough or choke. It gives a feeling of a less hot or “cold” spicy.

9. How Long Can Gold Wires Go?

Gold is universally used as an electricity conducting material. It is electric conductivity is not as high as copper, but it finds many uses thanks to being much more difficult to corrode (oxidize) than other metals. Besides, gold is extremely ductile. Only one ounce of metallic gold can be elongated into very thin wires of gold can be drawn into 80 km of wire! This makes the wire only five microns thick.

10. What Is a Rather Useless Property of DNA that Everyone Knows About?

A fun chemistry fact that I’ve seen circling around the internet ever since it went viral, after being published in 2013, is that apparently DNA is a flame retardant. What are the implications or the reasons behind this are still unclear, but still, something interesting to keep in mind.

11. What’s the Difference Between Caffeine and Theine?

Caffeine was discovered first from coffee (1819) by ta German chemist, F. F. Runge. The natural function of caffeine is to act as natural defense against insects, but also is a stimulant drug that makes us feel excited, making it easier for us to wake up in the morning.

However, the term “theine” is actually a way to refer to “caffeine” when it is in tea. But the molecule is exactly the same. There are other active components in tea that have stimulant effects, such as theophylline, but they are much weaker than caffeine itself.

12. What are Churchane, Housane, and Padogane?

There is a great highlight published by Prof. D. Trauner in Angewandte Chemie in which he discusses “the chemist and the architect”.

Human beings are constantly getting inspiration from any conceivable source. As Trauner puts it: “To imagine a structure and then express it in material form is one of the most satisfying of human activities. It is pervasive throughout the arts and crafts and it is one of the defining features of architecture. It is also at the heart of synthetic chemistry”.

Chemists had constructed plenty of structures that resemble real constructions, and named them after them.

13. Can You Put Out a Candle with Home Made Carbon Dioxide?

Of course you can just blow a candle out. You also probably know that you can put it out by covering it with a jar or other closed container that prevents oxygen from getting in and fuelling the flame.

There is actually a cooler way! You can generate a lot of carbon dioxide gas by mixing vinegar (acetic acid) with baking soda (sodium carbonate) in a glass. The mixture will start blowing out carbon dioxide, and you can pour carefully that gas (just the gas, not the liquid!) over a candle to put it out!

14. Can Table Salt Adopt Other Stoichiometry Than NaCl (1:1)?

Yes indeed it can. Maybe you haven’t seen this in your typical intorductory inorganic chemistry textbook. However, since 2013, several salts of sodium and chlorine were predicted to be stable: Na₃Cl, Na₂Cl, Na₂Cl₂ or NaCl₇. Some of these predicted structures were proved experimentally.

15. How Was the Structure of Benzene First Conceived?

Friedrich Kekulé conceived the idea of the benzene structure and its resonance forms after a dream in which he saw a snake seizing its own tail.

16. Can We Make Anthropomorphic Molecules?

Yes, many anthropomorphic (human-shaped) molecules have been made for fun by a team at Rice University, and they published in the Journal of Organic Chemistry.

The Nanoputians are molecules that resemble human beings, and were synthesized and diversified (to give different kinds of models, from scholar to a baker)

17. What Makes Up >99% of the Normal Matter in the Universe?

Helium and hydrogen make up most of the universe. Both of them account for 98% of all matter, being roughly 73% hydrogen, and 25% helium. All the other elements make up the remaining 2% of matter. The next in the list is oxygen, making up for a tiny 0.05%. Other atomic components in this order of magnitude are neon, nitrogen, carbon and silicon. We explore this with more detail here.

18. How Was Californium Made?

Californium was made in Berkeley, by the use of a 1.5 m-diameter cyclotron. As many other artificial elements, it was made by shooting He nuclei at curium-242 nuclei. This gives up to californium-245, an isotope with a half-life time of 44 minutes.

19. What’s Especial About Vanadium Oxide?

Vanadium oxide is a weird material which is a conductor of electricity but it is not a heat conductor. This was something completely unprecedented in the world of physics until it was discovered.

20. What Are Olympic Gold Medals Made Of?

They Olympic gold medals are not completely made of gold. In fact, they are made of at least 95% of silver, containing a minimum of 6 g of gold.

Gold is much more expensive than silver. However, thanks to this “tricky” alloy, a golden medal is just worth about $550, while silver medal is around $300.

Gold is around 100 times more expensive than silver, so a full-gold Olympic medal would cost $30.000! That’s why they only add enough amount of gold to give the medal the characteristic golden color.

A bronze medal, made of cheap copper and zinc, is actually worth only $2.

21. Do Chemists Know How to Make Drugs?

This is actually one of the most typical questions chemists get asked whenever they disclose what they do. Especially after the release of certain TV show…

And the short answer is clear: Yes, they do. Easily, in many cases.

That being said, it depends on the degree of experience and on the field in which you work on. Any undergraduate, working in any field, could probably follow experimental preps or “recipes” to make a common biologically active compound.

In case of somebody working on synthetic organic chemistry, with a MSc or PhD in that field, they can probably look up how to efficiently make any drug or derivative out there, with enough resources provided and access to a scientific database. This is obviously not limited to recreational drugs, but also to most small-molecule drugs that you take when you are sick.

22. What is an Alloy?

Alloys are basically combinations of two or more different metals, or metals with non-metals. Alloys are generally produced to obtain metallic materials with a given set of desired properties.

One of the most typical alloys out there is steel. Steel is basically a combination between iron (metal) and carbon (non-metal), which present very attractive properties.

Another example is the mixture of gold and silver used in Olympic golden medals. The resulting alloy is much cheaper than pure gold, but keeping the desired golden color for the medal.

23. How do Matches Work?

Match-heads are made of a combination of chemicals. The main ingredients are potassium chlorate, sulfur and glass. No phosphorus in the match head. Red phosphorus is basically what makes up the striking surface, along with more powdered glass or sand.

The main goal of the sand/glass present in both the match head and the striking surface is to cause heat through friction.

This amount of heat promotes the transformation of red phosphorus into white phosphorus. White phosphorus is incredibly pyrophoric. It can ignite spontaneously in the presence of oxygen from air, or from potassium chlorate itself. Sulfur (along with oxygen) keeps the flame burning. The wooden stick of the match does the rest.

Make sure to check out this infographic by Compound Interest:

24. How Does the Coke+Mentos Experiment Work?

This experiment went viral a couple of years ago. Adding “Mentos” to a bottle of Coke causes a large amount of pressure to build up. This basically makes the coke go flying as a soda geyser. You probably have heard of it:

But how does it work?

Why this happens has more of a physical explanation than a chemical one. The responsible process is called “nucleation”.

Coke, or soda, is filled with carbon dioxide (“fizz”). This contained CO₂ is dissolved into the liquid, and it wants out (it is a thermodynamically favorable process).

In the absence of Mentos (o whatever nucleation source you might use), this process goes on slowly. That’s why if you put the coke into a glass (which doesn’t have a lot of nucleation points, since it has an even surface), it doesn’t release a lot of CO₂ at once.

Your own mouth and tongue have a fair amount of nucleation sites: irregular spots where CO₂ bubbles can be easily released from the solution, that’s how you get the “fizzy” taste when you drink soda.

The surface of a Mentos is build up from a lot of microscopic layers of sugar, making it extremely irregular, full of crannies and nooks, which make up the perfect “nucleation weapon”. In contact with soda, this extremely irregular surface will make a lot of bubbles rapidly form, building up a huge pressure that results in the well known geyser!

By the way, we have covered how exactly to perform this science experiment here.

25. Why Are Graphite Rods Used in Nuclear Reactors?

Graphite is used in nuclear reactors as a moderator. Basically, a nuclear moderator decreases the speed of neutron release, allowing to control the nuclear chain reaction.

Carbon atoms in graphite can absorb the high kinetic energy that neutrons have when emitted in a fission process.

Nuclear fission reactors are based on the production of neutrons via fission processes.

Why would we want to slow down the release of neutrons? We want the neutrons to be captured by active nuclei such as uranium-235. For this to happen efficiently, without a nuclear moderator, we need to use enriched uranium (>3–5% of U-235). With a moderator, we can use natural or un-enriched uranium(LINK), much easier to access.

An alternative nuclear moderator is D₂O (heavy water), but graphite rods are usually preferred, since they are solid, cheap and occupies less volume.

26. Why Do Onions Make You Cry?

A relatively complex process takes place when you cut an onion. This results on the release of propanethial-S-oxide, which is an irritant of the lachrymal glands, which release tears.

In 2002 (Imani et al), it was reported that, upon cutting, onions release an enzyme called lachrymatory-factor synthase. This enzyme transforms sulfoxides present in the onion into sulfenic acid.

Sulfenic acid gets spontaneously rearranged into propanethial-S-oxide, which through the air, goes into your eye and irritates your lachrymal glands.

27. Why Does Ice Float on Water?

Ice floats on water because it is the least dense of the two.

As a general rule, out of two different substances or materials that do not react with each other, the less dense will float on top of the denser. The density of ice is around 10% lower than the one for water.

This property is extremely important for life. Rivers and lakes freeze from the top, so animals can still survive in the liquid water below. If ice was denser than water, it would sink, displacing water to the top, freezing as well as a result. This would result on the whole river/lake freezing, killing most forms of life living within.

28. Why Is Soap Used for Cleaning?

Soap is a mixture of amphipathic molecules, which have both a hydrophobic chain and a hydrophilic head. In water, these molecules such as fatty acid carboxylates, are arranged forming micelles.

Micelles arrange the hydrophobic chains towards the center, and the hydrophilic heads towards the outside (water). Hydrophobic molecules of dirt get “trapped” in the center. This allows an easy removal of apolar compounds from clothes or your skin.

These apolar components of “dirt” would otherwise stay, since they are not soluble in water.

29. How Do You Make Soap?

As mentioned above, classical soaps are made of fatty acid carboxylates. These are typically obtained from “saponification” of fatty acids with sodium hydroxide (NaOH), also known as lye.

One source of fatty acids is virgin olive oil, or coconut oil. Heating those up to around 100 ºC, and adding a water solution of NaOH gives the corresponding mixture of sodium carboxylates. Then, fragrances are usually added before the soap mixtures are poured into a mold and slowly cooled down to room temperature.

30. What Happens to Food While Cooking it?

If you have heard that cooking is chemistry, it is totally correct. Cooking is basically bringing chemical changes to food, mostly through heating.

When you cook a piece of meat, as you heat it up, proteins start to denature. As a result, you observe the typical color change, among other things. Also, collagen starts shrinking, pushing water out. This results in meat getting drier and drier the more time you cook it.

Another cool example is the use of baking soda while baking. This is basically sodium bicarbonate (NaHCO₃), which releases CO₂ upon heating, helping mixtures increase in volume or “rise” while baking them.

C&EN published a cool video about the chemistry behind cooking:

31. What Venom do Wasps and Bees Have?

Both wasp and bee sting venom is basically a combination of different enzymes and small molecules. The different enzymes have the goal of breaking down cells, including neurons, which is the cause of the intense pain that we feel. Smaller molecules present in the mixture enhance the effects of these enzymes, and make it last longer.

Although the effect of both venoms is similar, the enzymatic components are mostly different. That’s why some people can be allergic to one of the two but not to the other.

You can read further about this in our previous post about sting venom.

Furthermore, don’t forget to check out the list of most dangerous chemicals and poisons that we have put together on this other post!

32. Can You Turn Lead into Gold?

The short answer is yes, but not by chemical means, and the physical process is totally not worth it. Alchemy, the protoscience of chemistry, believed that it was possible to transform other metals into gold by the use of a “philosopher stone”. Now we know that is not possible, it was just myths and magic.

However, it can be actually done by using nuclear transmutation.

The difference between the two metals is the atomic number, defined by the number of protons they have in their nuclei. You can go from lead (it has 82 protons) to gold (it has 79 protons) by removing 3 protons from the nucleus. This can be straightforwardly achieved using particle accelerators. In fact, this is the way new elements are discovered, by using magnetic and electrical fields to accelerate particles, which then impact a starting nucleus. This impact can remove protons or neutrons from the nucleus, giving rise to new elements, or isotopes, respectively.

In summary, we can use physics to transform lead into gold, but the process is incredibly far from being economically viable!

33. Why Do We Put Salt Into Icy Roads?

This is due to colligative properties, specifically freezing point depression. When dissolving a salt, such as NaCl, in water, we can make its melting point go down from 0 ºC all the way to -20 ºC, or lower. This way, water will stay in liquid form even at sub-0 ºC temperatures, getting rid of ice on the roads.

34. Why Does Asparagus Make Your Pee Smell?

Asparagus have non-volatile sulfur-containing compounds. During digestion, we break down those compounds giving rise to volatile sulfur-containing chemicals, that can get to your nose through air. These compounds are smelly only to around 25% of the population: not all of us have the gene that allows smelling those compounds.

So, everyone produces those smelly volatile chemicals, but only a fraction of the population can actually detect them. we have posted also an entire account on this phenomenon, check out more about the chemistry behind asparagus!

35. Why Does the Planet Uranus, Rich in Methane and Hydrogen, not Burn?

Planet Uranus is indeed rich in extremely flammable gases, methane and hydrogen. But the burning of these gases requires oxygen. While we take oxygen for granted in Earth, Uranus simply doesn’t have enough for the flammable gases to burn.

36. How Does the Sun Burn without Oxygen?

Sun is made mostly of hydrogen (besides helium), which is a highly flammable gas. But, as in the case of planet Uranus, there is no oxygen at the Sun.

In classical terms, we need oxygen for a fire to burn. But the Sun is not actually on fire. Its heat and light come from nuclear fusion reactions, mainly combining hydrogen to make helium. This process does not require oxygen to happen.

37. Can You Burn a Diamond?

Diamonds are made of pure carbon, so it makes sense to think that they could burn under a oxygen atmosphere to produce carbon dioxide. But since the three dimensional arrangement of the diamond is so tight and difficult to disrupt, very high temperatures (in the order of 1000 ºC) would be required.

38. Can You Cool Pure Liquid Water Below Zero Degrees?

We have seen that adding other compounds to water, such as salts, allow us to decrease its freezing point. But what about pure water?

Yes, you can cool liquid water below zero degrees Celsius if you increase the pressure.

As you can see in the diagram, as soon as you go up from 1 atm of pressure, the melting point of water decreases.

39. What Is the Ozone Layer?

It is one of the layers in Earth stratosphere, around 10 km up from the ground. It has a high concentration of ozone (O₃). This gas is responsible for the absorption of most of the ultraviolet (UV) radiation coming from the Sun. Without it, the cases of sunburn, skin cancer or cataracts would increase dramatically.

40. What Is a Flame?

A flame is basically the part of a fire (an exothermic oxidation, or combustion generally by oxygen) that we can see with our eyes. The temperature or the color of flames depends of what is being combusted. Flame tests are performed in extremely hot flames, in which there are ionic gaseous components. These can be considered to be plasma.

41. Why Is Water Blue?

As some suggest, water is not blue due to the reflection of the sky. Water is blue on its own. Any object shows a given color because it is absorbing visible light from some other wavelength preferentially. Water has a weak absorption band in the red part of the visible spectra (close to the infrared zone). For this reason, water shows a blue color. Since this red absorption band is so weak, we can only observe the blue color if we have a massive volume of water. That is why water in a glass appears to be colorless, but bigger volumes such as oceans, lakes, or swimming pools, are blue.

This reading in the Journal of Chemical Education is highly recommended if you want to expand further on the subject.

42. What Is the Difference Between Glass and Crystal?

Although some people may use these words interchangeably, they are not the same. In fact, both things are somehow opposite by definition. A crystal is a solid substance that presents a highly ordered arrangement of its microscopic components. On the other hand glass is an amorphous non-crystalline solid, which are usually produced by rapid cooling of melted amorphous materials, such as silica, or SiO₂.

43. Can You Burn a Metal?

You definitely can burn a metal. Some examples are thermite (in which you are basically burning aluminum) or fireworks.

44. Are Two Atoms of the Same Element Exactly the Same?

Two atoms of the same elements are exactly the same if and only if they have the exact same molecular, atomic, electronic and nuclear states. This is extremely difficult to achieve, so much so that a physics Nobel prize was awarded on this regard.

For example, sodium and chloride from NaCl are the same elements than of metallic sodium or chlorine gas: their molecular/atomic state is completely different.

Another example are different isotopes of the same atom. Not all bromine atoms in NaBr are isotopically the same. Some have 79 neutrons on its nucleus and some have 81.

45. What Is the Origin of Life?

This is an extremely complex question to answer, but chemistry sure is central to this phenomenon. The origin of life is basically the transition from chemistry to biology, at it is estimated to have happened on Earth around 4000 million years ago, when gaseous water first condensed to give liquid water.

46. Is There Any Liquid Metal at Room Temperature?

Yes. The only metal liquid at room temperature is mercury. In fact, mercury stays a liquid until it is cooled down below -39 ºC. Gallium is also a fun metal. Its melting point is 30 ºC, so it stays solid at room temperature but it melts at the 37 ºC of your hands!

Do you want to know if you could stand on liquid mercury? Take a look at this video!

47. Why Do Some Balloons Float?

They float if they are filled with a gas significantly lighter than air. Helium is less dense than air. Therefore, helium balloons will float. On the other hand, air-filled balloons will not float due to the weight of the balloon’s rubber itself.

48. Why is Mars Red?

The red planet gets its name from iron oxide, or rust, Fe₂O₃. Mars is covered with this orange-red material. If you see the sky from Mars, it will appear light orange due to iron oxide particles suspended on its atmosphere.

49. Why Do Storms Smell Like Ozone?

Ozone (O₃) has a particular smell, which you can smell after heady rains in thunderstorms. Lightning heats up the air to the level of 50.000 degrees Celsius. This extreme conditions can cause some of the oxygen (O₂) of the air to recombine into ozone, which we can smell.

Nature creates ozone through lightning and sunlight:

50. Is Glass a Solid or a Liquid?

Glass is not a liquid; it is an amorphous solid. With amorphous we mean that it has no microcrystalline order. With solid we basically mean that you can grab it without losing its shape.

51. How Old are Hydrogen Atoms in Our Body?

Hydrogen atoms, together with helium atoms, were created right after the Big Bang. This happened around 13.7 billion years ago! So the hydrogen atoms that make up your body are 13.7 billion years old.

52. Can You Freeze Air?

Yes, you can. Air is mainly a mixture of nitrogen gas (N₂) and oxygen gas (O₂). Their freezing points are -210 ºC and -219 ºC respectively, so below -220 ºC, air would freeze. This has been achieved by using liquid helium. Helium, however, is the only known gas that does not freeze. Helium liquefies at -270 ºC.

53. Can a Substance Solidify Upon Heating?

Apart from complex mixtures, such as certain foods, which can solidify upon heating (for example, an egg), there are examples of simpler liquids that defy the rules, and freeze upon heating. A mixture of two organic components which is liquid at room temperature, solidifies in the range from 45 to 75 ºC. The mixture takes the state of a sol-gel.

54. Can We Reach Absolute Zero Temperature?

Absolute zero (0 K or -273.15 ºC) is a theoretical minimum, in which atoms would stop moving, and cannot be achieved. However, thanks to cryocooling refrigeration techniques, we can come close, in the range of a billionth of 1 K. Surprisingly cold! But never absolute zero.

The idea of absolute zero was actually pioneered by Robert Boyle himself!

55. Why Does High Air Humidity Make it Feel Hotter?

The natural mechanism of our body to cool itself down is sweating. Evaporation of sweat from our skin takes up energy from our bodies, cooling ourselves down. The more water there is already in the air (higher humidity), the more difficult this evaporation process take place. Therefore, higher concentration of water on air, makes us feel hotter because we cannot cool down efficiently.

56. Can You Die for Drinking too Much Water?

Hyponatremia (which means “low in sodium”) is what water intoxication is called. Approximately, drinking 6 litters of water in a relatively short time, can cause serious injuries, even death! This happens because huge amounts of water make your blood concentration of sodium (or other electrolytes) drop drastically, making your cells accumulate too much water inside, swell, and even rupturing.

This would happen more easily if you drank distilled water (which is not dangerous in small amount, just as regular water).

57. Why Car Airbags Are Filled with Sodium Azide, a Very Toxic Substance?

Airbags are actually not filled with some compressed gas. Chemistry takes action when airbags inflate. They are filled with around 100 grams of sodium azide (NaN₃), which upon heating (which is triggered by an igniter that goes off upon collision detection) decomposes to give N₂ gas (more than 50 L, enough to fill a typical airbag) and sodium (Na) metal. Since sodium metal is potentially explosive, the airbags also contain several compounds that would react quickly with sodium, to avoid any danger.

58. How Many Molecules Are in a Rubber Tire?

In a nutshell, you could say that it is just a large single molecule, a polymer with a huge molecular weight. In reality, it is a bit of a grey area, and calling it a single molecule is misleading.

Rubber tires are actually made by combination or binding of different polymeric chains. These are combined together in the process of vulcanization in which sulfur present in these chains forms covalent bonds that attach the polymeric chains together.

This process basically links all the individual chains, forming a cross-linked network. You can say that the result is a single molecule. However, a more accurate description would be defining this kind of polymers as “molecules-of-molecules”.

59. Why Does Water Expand when Freezing?

This is mainly due to hydrogen bonding in water. Water behaves weirdly because of this. From 4 ºC (when it reaches the maximum density) above, water behaves “normally”, expanding upon heating and contracting upon cooling. In the 0–4 ºC range, it actually contracts upon heating.

As water goes below 0 ºC, crystalline networks of ice form, in which the orientation of hydrogen bonding changes, arranging water molecules further away from each other. This results on ice being less dense than liquid water.

60. Who Discovered the Periodic Table?

The first disclosure of a periodic table as we know it today, which celebrates its 150 anniversary in 2019, was made by Dmitri Mendeleev in 1869. He published an arrangement of the known elements by the time ordered by atomic mass. This allowed, not only prediction and understanding of properties, but also to predict the discovery of empty blank spaces in his original periodic table!

61. How Does Helium Change Your Voice?

Sound travels though helium, a lighter gas, much faster than it does through air, a heavier gas. Sound travels around 2-3 times faster through helium, making high frequencies sound louder than low frequencies, making your overall voice sound higher in a funny way.

If you were to do the opposite: inhaling a gas denser than air, the effect would be your voice sounding lower for the exact same reason.

62. How Did We Discover that Diamonds Are Made of Carbon?

The discovery of the composition of diamonds is attributed to Antoine Lavoisier, at the 18^th century. Lavoisier built a solar furnace, which is a tool that is used to focus sun rays. This technique allowed him to burn a diamond. Analysis of the resulting residue let us learn that the composition of the diamond was simply carbon, common coal. The work carbon comes exactly from French coal “charbon”.

63. What Would Happen if you Peed in Space?

This works for water, or any kind of aqueous solution such as pee. If you put water outside your spaceship, even though it would be dramatically below its freezing point, it would vaporize and go into gas phase right away. This is because of the lack of air pressure there is in space. It would be like submitting it to very high vacuum.

Nevertheless, eventually, it would freeze, but not before turning into a gas first!

64. What Is Dry Ice?

Dry ice is basically the name we use for solid (frozen) carbon dioxide, or CO₂. It has a surface temperature of -78 ºC, and it is widely used as cryo-cooling agent.

65. What Color is Oxygen?

As a gas, elemental oxygen (O₂) is colorless, odorless and tasteless. However, if you cool it down enough to liquefy or freeze it, it becomes pale blue.

This is due to oxygen becoming paramagnetic when it condenses into liquid or solid phase. The unpaired electrons originate a “magnetic asymmetry” in the molecules. This creates a absorption band in the visible spectrum (very much as why water is blue), which absorbs red light, resulting in a blue color.

In another post, we have covered the color of oxygen and its properties in more detail.

66. What Happens When You Add Table Salt to a Volume of Water?

Volumes are not always additive. When you add table salt, or NaCl to water, you are increasing the density of water. This happens due to positive interactions between water molecules and Na⁺ and Cl^– ions.

Since the resulting mixture is denser, the total volume will decrease and be lower than the actual sum of water volume and added salt volume.

67. What Happens if You Mix Half a Liter of Alcohol and Half a Liter of Water?

This is another example of non-additive volumes. Positive interactions between water and alcohol (ethanol) molecules, make the resulting mixture occupy less than 1 L of total volume. You can think of it as if you mixed two substances which molecules can be easily held between the molecules of the other species. Imagine mixing 0.5 L of sand and 0.5 L of water. The resulting mixture will barely occupy more than a single half liter. For this case is the same, although at a much lower extent.

68. Can You Taste Food without Saliva?

Our mouth taste receptors are made to work by detecting dissolved substances. If you don’t have saliva to dissolve the molecules in food responsible for its flavor, you will not be able to taste it.

69. What Color is Lobster Blood?

Lobsters have blue blood. As you know, vertebrates and most other animals have red blood. This red color comes from hemoglobin, which is basically a protein containing an iron-porphyrin coordination complex. On the other hand, animals such as lobsters have a different protein, called hemocyanin. This protein has an active site which contains a coordinated copper atom, responsible for the blue color. This is also the case for other animals, such as snails and other mollusks.

Check out this summary about the origin of the different colors of blood!

70. Can Goldfishes See Colors?

As surprisingly as it may seem, goldfish have a very specialized vision in which they rely on for finding food. Human beings can only see three primary colors (red, yellow and blue). However, goldfish see a fourth primary color (they are tetrachromate), which is part of the ultraviolet spectra. This is also the case for the zebrafish.

Being able to see UV light allows these animals to detect very subtle movements in water, helping them find prey, such as shrimp or worms.

71. Why Do Fresh Eggs Sink, and Rotten Eggs Float?

A classical trick to know whether we can still eat an egg (if they are fresh enough) is putting them in a bowl of water. If the egg sinks, it means that it is still denser than water, which is the natural state if they are still fresh.

As decomposition takes place, solid and liquid matter is transformed into gas. Gaseous pressure builds up, and since the egg shell is porous, this gas starts escaping. This loss of mass, eventually leads to the density of the egg being lower than water’s. This makes the egg float. This represents an easy way to tell if an egg has undergone too much decomposition to be eaten (if it is rotten).

72. How Hot Does a Lightning Strike Get? Is it Hotter than the Sun?

Lightning is incredibly hot! They can reach temperatures of around 30.000 ºC, which is around 5 times the temperature of the surface of the Sun. Keep in mind that this is just its surface, the core of the Sun reaches several million degrees, which is much more than lightings.

73. Why Does Wildfire Spread Uphill Quicker than Downhill?

A fire needs a combination of fuel (the trees) and oxygen to keep going. This combination is fed more easily to the fire if it is moving uphill, when the fire from the top of one tree can start burning the bottom of the next one, which is in a place with much more available oxygen and unburnt material. Picture how matches burn: they also burn much faster if held upside down than if you leave it the correct way. The case is very similar with forest fires.

74. Do Frogs Need to Drink?

Frogs do not need to drink using their mouths. The absorb water through their skin. They have a skin-area called “drinking patch”, on their bellies, which they use to get all the water they need.

75. What is the Hardest Chemical in Your Body?

The hardest substance on the human body is enamel, the external tissue that covers teeth. It is made up almost exclusively by minerals, being calcium phosphate the main component.

76. What’s the Role of Ethylene in Fruit Ripening?

Ethylene is a gas that acts as a growth hormone for plants. It can be released by plants and fruits, and at the same time, it regulates processes such as aging or ripening. Ripening is basically the set of changes that fruit undergoes over time: generally softening, and changes of color or texture. These changes can be triggered by ethylene. An example of a fruit that produces a lot of ethylene are bananas. This is why storing other fruits near bananas, will make them ripen faster.

77. What is the Mole Day?

The mole day is a sort of funny celebration day for chemists, which takes place on October 23 between 6:02 am and 6:02 pm. This makes the date to be 6:02 10/23. This celebrates basically Avogadro constant, which is roughly 6.02·10²³.

78. Do Metals Have Antibacterial Properties?

Yes, some metals (in their actual pure metallic form, not as salts or complexes) do have antibacterial properties. The most common one is copper, or alloys of copper, these metallic substances are natural antibacterial compounds. It was also found more recently that other pure metals, such as titanium, zinc, or nickel also have antibacterial properties.

79. Can We Freeze Helium?

Helium is the only known substance that cannot be frozen at atmospheric pressure. However, under pressures higher than 20 atm, liquid helium (which is usually employed to cool down to cryogenic pressures, and is able to freeze other gases), can be pushed into the solid phase. Helium melting conditions are located at 25 atm and 0.95 K, which is less than 1 degree above above absolute zero temperature!

80. Is There Helium on Earth, and How Do We Collect It?

There is a lot of helium on the universe. In fact, it is the second most abundant element next to hydrogen. However, it is not that abundant on Earth. But still, there is some, and it is located underground. It is basically extracted in the same process that we use to get natural gas from mines. The amount of helium present in natural gas is then separated using cryogenic separation processes.

81. How Much Carbon Is in the Human Body?

We can make a lot of pencils with the carbon in each of our bodies! Roughly 20% of the human body is carbon. Taking an average adult of 70 kg, that gives you around 14 kg of carbon. If that amount of organic carbon was transformed into graphite, we could make almost 10.000 pencils (which contain 1–2 grams of graphite) out of it.

82. Do Mosquitoes Bite More Girls than Boys?

A widespread idea is that mosquitoes are generally more prone to bite women than men, because estrogen can attract them. This is not really the case according to a study: the main factor playing a role here is heat emission. Mosquitos get to you following the heat that our bodies emit. Also, higher emission of carbon dioxide correlates with a mosquito wanting to bite you more, as well.

Larger people usually emit more heat and CO₂, so these will usually be bitten by mosquitoes most. Men are usually larger than woman, so they would be bitten more often.

Similarly, pregnant women, who exhale more CO₂ and usually show higher body temperatures, can be easily detected by mosquitoes.

83. What Is the Softest Substance?

It is common knowledge that the hardest material known on Earth are diamonds, but defining the softest is not as simple.

Softness is the tendency of a substance to get deformed (and stay deformed) when pressure is applied to it.

The classical test to evaluate hardness/softness is Mohs test, in which two materials are rubbed against each other, to see which one scratches which. According to this test, talc, a mineral made of hydrated magnesium silicate, defines the softest point in the 1–10 Mohs scale.

84. What Is the First Element Ever Created?

The first Nature-made elements were helium and hydrogen. They formed after Big Bang, within an extremely hot environment, as a result of combination of subatomic particles. Quarks combined, originating protons and neutrons, which got together giving nuclei. Then, electrons eventually combined with nuclei, creating the first hydrogen and helium atoms. As for the first human-made element, the answer would be technetium.

85. Which is the Heaviest Element in the World?

In terms of density, the heaviest element is osmium (22.59 g/cm³), followed closely by iridium (22.56 g/cm³).

In terms of highest atomic number, it is something that changes every time a new, heavier element is discovered. The natural element with the largest atomic number is uranium (with an atomic number of 92). However, many synthetic heavier elements have been discovered, being oganesson, previously known as ununoctium, (atomic number of 118) the one that holds the first place. It was first synthesized in 2002.

86. What Is the Rarest Element on Earth?

Out of all the natural elements on Earth, the fifth halogen, astatine, is the least abundant one. It is so rare that only 30 grams of astatine can be found in our entire planet!

87. How Dangerous is Hydrofluoric Acid?

Out of all of the hydrogen halides, HF or hydrofluoric acid is actually the least acidic, but it is also arguably the most dangerous. It can not only be fatal if swallowed or breathed, but also very dangerous in contact with your skin. HF can easily go through our skin, attacking and heavily damaging our tissues (including bones) from the inside.

Check out some experiments by Periodic Videos:

88. How Much Gold Is There on Earth?

The usual estimation says that there is around 170.000 metric tons of gold on Earth. This amount would fit in a cube sized around 21×21 meters.

89. Why Do Coins Have a Smell?

Coins, and metals in general, actually don’t have a smell. Our own bodies are responsible for the typical “metallic odor” that we associate with them.

Upon contact with some metals (including iron), 1-octen-3-one is formed as a result of the decomposition of oils present in our skin. This chemical is the real responsible of the smell that we associate coins or metals with.

90. Why Gold Does not Present a Silvery Shine as Most Metals?

This is not an easy question to break down in a few lines. The answer relies on quantum chemistry and relativistic effects.

Most metals have no color, in the sense that they do not absorb photons on the visible light wavelength range. They reflect all the visible light, resulting in the typical silvery shine. Further reading.

However, due to relativistic effects, some of the outer electrons of gold atoms, move much faster than usual. This quantum effect shifts the absorption range of gold so it covers some of the visible spectrum. Like so, gold can absorb some blue light while it reflects the rest of the visible light, resulting in this shinning yellow or golden color.

91. What’s Special About Gallium?

Gallium is a metal with an unusually large liquid state range, which goes from 303 degrees Kelvin (30 ºC, that’s why it melts in your hands) up to 2477 K. This is because it has a significantly anomalous crystal structure compared with most metals.

Check out how body temperature can melt gallium!

92. How Many Water Molecules Are in a Bucket?

Let’s say we have a 1 L bucket of water. One liter of water is roughly 1000 grams, which translates into 56 (1000 g/18 g/mol) moles of H₂O. If we known that each mole of a compound contains around 6.022·10²³ molecules of that compound (Avogadro’s constant), we will have 3.37·10²⁵ water molecules inside the 1 L bucket. This number is around 4000 times larger than the estimated number of grains of sand on the entire Earth!

93. Does the Hole in the Ozone Layer Still Exist?

The layer of ozone present on the stratosphere protects us from most dangerous UV radiation coming from the Sun.

Over the 1980’s and 1990’s, a hole (more accurately, a zone of partial depletion or lower ozone concentration) in this layer was dangerously growing in size, as a result of people abusing the use of CFC (chlorofluorocarbons) compounds.

Fortunately, after prohibition of many substances that were damaging the ozone layer, the hole present over Antarctica started to shrink, going back to the size that it had before the 1980’s.

94. What Is the First Time that Chemistry Has Been Used?

Modern chemistry, together with modern science in general, it’s a relatively new thing. But human kind has been using chemical processes even by 1000 BC! Technologies such as extraction of metals from ores, medicine from plants or fermenting wine, are nothing more than chemical processes, discovered by people thousands of years back.

95. Can We See Atoms and Molecules?

Yes, thanks to techniques such as atomic force microscopy. You can consult our account on the imaging of atoms and molecules by those techniques.

96. Can Molecules Walk?

Yes! The team of Leigh and coworkers has reported molecular machines that appear to be walking at the molecular level. A video is worth a million words: If you have time and you are really interested in a subject that got awarded the Nobel Prize in 2016, take a look at this lecture by Prof. David Leigh. Watch out for the magic tricks

97. How Did They Come Up with Coca-Cola?

John Pemberton, an American Civil War veteran, who was wounded during this period, dedicated the rest of his life to the development of a new medicine to use as painkiller. Most of his attempts were unsuccessful, expect for a beverage based on the coca plant, which helped calming nervousness. Pemberton sold the recipe to a businessman before he died, who turned into the drink that we all know today.

98. What is More Complex, the Universe or Chess?

As it is agreed by most physicists, the entire universe is made up of about 10⁸⁰ atoms. This is a 10 followed by a lot of zeroes. A gigantic number. However, a mathematical estimation of the possible moves that could happen in a game of chess, found it to be 10¹²⁰. This points to chess not being so boring as it may seem…

99. What Happens if You Clean Your Hands with Bleach?

When you make alkalis as lye react with fatty acids, you get soap. If you use alkalis, such as bleach to wash your hands, something similar is happening. You are turning the fatty acids in your hands into soap, making your hands weirdly smooth and slippery. Now you are turning your hands into soap!

100. Are We Made Mostly of Empty Space?

Human beings are made of organs, proteins, molecules, atoms. Atoms. We are made of atoms, which on themselves are actually made of almost nothing: empty space. Apart from the subatomic particles, (neutrons, protons and electrons), the volume of an atom is >99% plain empty space. Then again, these atoms are held together by different kinds of atomic forces, so, if the basic units that build us up are empty atoms… We are literally made by >99% of empty space!

I leave you with this quote from the Institute of Physics:

101. BONUS: Should I Trust an Atom?

Never! They make up everything!

(Hint: you can check a t-shirt of this fact on this list of chemistry gifts)

Hope You Have Enjoyed Our List of 100 Fun Chemistry Facts!

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Be sure to discuss in the comment section whatever you want us to look further into!

We appreciate any feedback.

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Why Use an AP Chemistry Review Book?

Why wouldn’t you want a comprehensive study guide to help you prepare for one of the toughest exams you will take in high school? You’re going to be studying anyway, so it makes sense to use an AP chemistry review that is actually designed with your particular exam in mind.

Besides from learning chemistry, we are aware that acing exams is also important for students.

The best AP chemistry study guides are updated each year to reflect the changes that are sometimes made to the AP chem exam, and they are a great value, especially when you consider how much more efficient your study plan will be. It’s definitely cheaper than the college chemistry class you’ll have to take if you don’t pass!

If instead of AP chemistry exams, you are preparing the chemistry SAT subject test, check of this other guide.

Furthermore, all the 2020 edition has been recently released for most of these review books. Get your hands now in a completely updated text and get ready to ace your AP chemistry exam in 2020!

As a side note, if you are simply interested in “self-learning” chemistry, check out this other review on the best chemistry books for self study.

The Best AP Chemistry Review Book for 2020

Let’s cut right to the chase with what is, in our opinion, your best choice for an AP review book this year: Cracking the AP Chemistry Exam 2020 Premium Edition: Practice Tests & Proven Techniques to Help You Score a 5, from The Princeton Review.

Why we like Princeton Review’s AP chemistry book:

Cracking the AP Chemistry Exam 2020 checks all the boxes for us. The study guide is well organized, follows the most updated AP chem curriculum, and offers good advice on creating a study plan and test taking skills. Information in the book is clear and concise, and the publisher has a solid track record of eliminating content that no longer appears on the exam.

Each chapter ends with some multiple choice and free response questions for you to practice and test your understanding. In addition, the book includes two full-length practice tests with questions that are similar to what you’ll see on exam day. Among the two editions (regular and premium), we recommend going directly for the premium one, since it has a lot of extra practice activities. See each review below for more information.

Summary Table

In the following table, you can see a general overview and do a quick comparison between the different review books available.

You have not decided yet? Keep reading!

Top 10 AP Chem Books to Consider

You have plenty of options to help you study for your AP chemistry final. Here, we have a top 10 list of the best AP chemistry textbooks, review books and related resources.

Cracking the AP Chemistry Exam 2020 Edition: Practice Tests & Proven Techniques to Help You Score a 5

For years, this study guide from The Princeton Review has stood out because of its balance between comprehensive information and efficient studying, and it’s our top pick for many reasons. Explanations in the content review and practice test solutions are concise without bogging you down in unnecessary details. With end-of-chapter questions and two full-length practice exams, you’ll have a good idea of what to expect on test day.

Strengths of this book are:

• Good advice on study strategies
• Targeted test taking skills for the different types of questions
• Full “main concept” review based on the latest AP chem curriculum
• Online tools including updates to planned changes for the 2020 course and exam
• Numerous and varied practice questions with complete explanations
• No outdated content that no longer appears on the exam

With these strengths in mind, the conciseness that some students see as an advantage in this book might be a drawback for others. If you require more in-depth explanations of the material or more detailed solutions to calculation-heavy practice problems, a different book might be better for you.

Even if you choose another book as your primary resource, we would strongly recommend Cracking the AP Chemistry Exam 2020 as a supplement based on the quality of the practice exams alone.

Barron’s AP Chemistry with Online Tests

This book is another longtime favorite among students thanks to a generous amount of practice questions, online content, and very detailed concept explanations.

Advantages of Barron’s review book:

• Lot of practice questions, 3 practice tests and 3 online tests
• 3 diagnostic tests to identify weak areas
• Detailed review and explanations
• Tips on answering free response questions

However, people who have used this ninth edition (as well as previous ones) complain that there are errors in the study guide, practice problems and answer keys. Although there are many practice tests, the questions can feel repetitive, focusing too heavily on certain concepts at the expense of others. Finally, this publisher only releases new editions every two years, so it is likely not as up to date as Princeton Review; depending on how you look at it, this book either overprepares you for the exam or wastes your time with material that you will not actually need.

If you choose to use Barron’s AP Chemistry, make sure you study the content review in addition to doing the practice tests to fill in any gaps. We would also suggest getting the companion flashcards.

Barron’s AP Chemistry Flash Cards Third Edition

These are intended as a complement to Barron’s AP Chemistry textbook. Among the various flashcard options available for this course, these are some of the best rated, and students have found them quite helpful. If you like reviewing with flashcards, this could be a useful study tool for you, but it isn’t a replacement for the full-length practice exams you find in the book.

It is a very good idea to use these cards to supplement what is covered in the Barron’s textbook. Some students complain of gaps in the concepts covered in Barron’s practice tests and review material, and this is one way to try to fill in those gaps.

AP Chemistry Crash Course Second Edition Book + Online

This book is exactly what it says it is: a crash course. It’s great for a quick review with material that has a very narrow focus on what actually appears on the final exam, as well as helpful strategies for answering the different types of questions.

Because of its laser focus on the exam, if you want a study guide that can also help you throughout the school year with assignments and your teacher’s tests, you will probably need another book instead of or in addition to this one. The explanations are complete but also concise, and they might skip over things your teacher covers in class because they aren’t important on the AP chem final.

On the downside, the latest edition released for this book was in 2014, and the official curriculum and test content has changed since then. It is also lacking in practice questions, which are very important to feel prepared on the day of the exam. But for a cheap price, it wouldn’t hurt to use AP Chemistry Crash Course as a supplement.

Cracking the AP Chemistry Exam 2020 Premium Edition: 5 Practice Tests + Complete Content Review

You may recognize the title from #1 on this list. This is, in fact, the premium edition of the same book. What does that mean? It has all the pros and cons described in that first review: comprehensive content review of all the topics that are tested under the current curriculum, test taking tips, study strategies, updates on course changes for the 2020 school year, practice questions of various types at the end of each chapter, etc.

What makes this edition “premium” is that is has extra practice tests. Whereas the standard edition comes with two full-length practice exams, this premium edition comes with four tests in the book itself and a fifth one available online. Just like in the standard edition, all the premium edition practice tests come with detailed answer explanations.

Two tests may very well be enough for some students, but this is an excellent alternative if you are someone who doesn’t believe there’s such a thing as being overprepared.

Sterling Test Prep 2020 AP Chemistry Practice Questions: High Yield AP Chemistry Questions & Review

The highlight of Sterling Test Prep 2020 AP Chemistry is right on the front cover: “Higher score guaranteed!” They claim to offer a money back guarantee, but there is little further explanation except that they value customer feedback and answer all emails. More promising is the fact that they offer a small reward to anyone who reports a mistake, typo or grammatical error, so the quality of the material is very high.

But it’s very important to realize that this book is not a content review book. It contains diagnostic tests and 900 practice questions will full explanations, but that’s all. If you want material to read through before taking a practice exam, you will need to supplement. You could use another book from this list, or you could use Sterling Test Prep’s companion book, AP Chemistry Complete Content Review.

If your opinion on practice questions is “the more, the better”, this book might be right up your alley. And if you want even more questions, you can purchase access to Sterling’s online test platform, at a discounted price if you have purchased the book. But be prepared to buy additional materials if you want to study the content before practicing.

One last caveat to this review book: the practice questions are all multiple choice. A significant portion of the AP chemistry exam will be written response, so if that is a concern for you, this might not be your ideal study resource.

5 Steps to a 5: AP Chemistry 2020

This is another highly rated review book for AP chemistry that offers a good balance of conceptual information, study strategies, and practice opportunities. If you have ruled out our #1 choice for whatever reason, this would probably be our second pick.

5 Steps to a 5 is well organized and aligns with the 2020 AP curriculum, focusing on material that you will need to know for the final exam. Its content review is complete and easy to understand, and each chapter includes important equations, a glossary, and practice questions.

Probably the most impressive thing about this option is its “cross-platform prep course”. It caters to digital natives by offering two practice exams in the book, two more online, and a mobile app that students can use to create a study plan (although the study planner app can be a bit glitchy). Plus, the platform provides you with “powerful analytics you can use to assess your test readiness”, as well as flashcards and games.

5 Steps to a 5: AP Chemistry 2020 Elite Student Edition

Same as the previous book, but with a fun extra feature to help reinforce material every day during the school year. In addition to the book/online/study planner app (what the publisher calls their “cross-platform prep course”), you also get access to the “5 Minutes to a 5” tool.

This premium feature gives you 180 bitesize reinforcement activities (one for each day of school) to help you study a little bit every day. Obviously, this is a better way to prepare for the exam than cramming at the last minute, but it is most useful if you buy it early in the school year. If finals are right around the corner and you’re just starting to look for an AP chemistry review book, you might be better off with the regular edition of 5 Steps to a 5.

Zumdahl, Zumdahl & DeCoste’s Chemistry Tenth Edition

This is more of an AP chemistry textbook than a review book. Strictly speaking, it’s a college chemistry textbook, which explains the price. We have also previously disclosed some exhaustive reviews of the best organic chemistry textbooks. College textbooks are infamous for their exorbitant costs. However, if you want to be able to explore chemistry in depth and the textbook your teacher is using doesn’t meet your expectations, Zumdahl’s Chemistry is an option to consider.

Furthermore, science books like these usually don’t change much from one edition to the next, so if you can find an older edition at a lower price, there’s probably no harm in choosing it over the latest version.

You might also want to go all-in and go for one of the best general chemistry textbooks that we reviewed. This option will be great if you plan in taking chemistry courses in college!

Study Guide for Zumdahl, Zumdahl & DeCoste’s Chemistry Tenth Edition

If you decide to spring for Zumdahl’s Chemistry textbook, you might also like to take a look at its companion study guide. It’s not very useful on its own, but combined with the main book it will help you stay engaged and give you some guidance in what would otherwise be a very independent learning process.

Final Thoughts on Choosing the Best AP Chemistry Review Book

You’ve got many and varied options to study for your AP chem final with this top 10 list of review books. Everyone’s needs are different, but we can recommend The Princeton Review’s Cracking the AP Chemistry Exam 2020 as a great resource that will be helpful and accessible for most students, or the premium edition for even more practice exams.

Along with the premium editions of 5 Steps to a 5 and Cracking the AP Chemistry Exam 2020, we add as our top complementary recommendation Zumdhal’s Chemistry textbook, filling up the top 3 choices. Keep in mind that, even if you buy Zumdhal’s Chemistry, you will still need one of the two first ones to prepare for the actual exam.

With these picks, you’ll get more bang for your buck compared to Barron’s or Sterling, which work best when supplemented with additional study tools.

Whatever you choose to help you prepare, order your study materials now (or preorder the 2020 edition if applicable) and use them as a guide throughout the school year. Best of luck!

The post The Best AP Chemistry Review Book appeared first on Chemistry Hall.

But out of ALL of them, how do you choose the best one? The amount of material out there is overwhelming. But don’t worry!

No matter if you are a student, a chemistry or research professional, a university professor, a parent, or a high school teacher, there is always a good organic chemistry book for you.

In this exhaustive review we will help you buy the textbook you need!

Which is The Best Organic Chemistry Book?

If you don’t want to look further and go straight for the top 1 pick for most situations, “Organic Chemistry” by Clayden, Greeves and Warren is definitely the best textbook for most needs.

Top-notch learning approach, easy to follow, with plenty of “real-life” examples, enough practice problems, and beautiful graphics. If I only had to choose one, this would be the best organic chemistry textbook there is: Clayden’s Organic Chemistry

Clayden’s Organic Chemistry is never going to fail you as a chemistry textbook. If you want an organic chemisty textbook for self study, this will also be great. However, you might be looking for something different. Or for a different teaching approach. Or maybe you are looking for something more advanced that will be worth consulting from years to come. I have many of the books on this list sitting in my office these days, and my undergraduate days are long gone.

Keep reading and you will find your most appropriate recommendation!

Summary Table: Top 13 Textbooks

In the table that follows, you can see a quick description of each book. This way you can know if it fits your needs at first glance.

Not decided yet? Don’t worry! The most complete and exhaustive review on the internet of the best organic textbooks follows.

Furthermore, if you are looking for the best complement for learning organic chemistry, check out our review of the best organic chemistry model kits.

Complete Review of All Books

1. Clayden Organic Chemistry

As we have already clearly said, Clayden’s is going to be the best book for organic chemistry in most situations. This book is authored by Jonathan Clayden, Nick Greeves and Stuart Warren. It’s basic enough that if you are just getting started studying organic chemistry you will be able to catch up. But also covers topics from most advanced organic chemistry courses.

If you are professor, it is also going to be a solid bet for planning lectures. And besides, it is a great organic chemistry reference textbook for any chemist. This book sits on my shelf since I started studying undergraduate chemistry, and it always have a place there. Also it is one of the few affordable stand-alone chemistry textbooks out there.

Many consider Clayden as the best book for organic chemistry. Clayden emphasizes on concepts, and binding those concepts together, building up in top of each other. The first edition was published in 2001, but the last one (2012) covers greatly the most relevant topics in organic chemistry of the last years, such as the palladium catalyzed Suzuki or Heck reactions, or the Grubbs metathesis reaction (all of them awarded the Nobel prize).

A progressive way for fundamental understanding

If you want to really understand the fundamentals behind organic chemistry, Clayden’s is the clear superior choice. Most of other textbooks are structured about functional groups, and the sets of reactions that you can run to make it or to get to them.

On the other hand, Clayden starts off by introducing a very simple and common reaction: addition reactions to carbonyl compounds. Then goes over different carbonyl reactions, such as substitution or condensations (reactions with the loss of water). This smooth progressive mechanistic approach makes Clayden’s stand our among all organic chemistry texts, which are generally more “plain” and rely on individual chapters for individual types of molecules.

Clayden: Rich contents, visually appealing and entertaining:

This brilliant textbook is one of the few that make good use of colors as a visual learning tool. This, in my opinion, should be mandatory for any good organic chemistry textbook published after 2010.

The style of the book is quite unique. It is written in an informal and honest way that makes it extremely pleasant to follow. Furthermore, many examples based on interesting/famous molecules or chemical problems are presented throughout the book. The only drawbacks that I can think of is that some of the final chapters, such as the ones for organometallic chemistry, would be better off if they were a bit more expanded. Also, there are no in-chapter problems. Finally, as you can see, the last edition is from 2012; if getting a very up-to-date textbook is in your top priorities, maybe you should look into other texts.

Otherwise, Clayden is clearly the superior tool for learning organic chemistry. Remarkably, they use the molecular orbitals theory as a model to rationalize explanations for the very beginning, which is great for learning purposes.

Overall, Clayden organic chemistry textbook is a perfect blend between good contents, great formatting and both educational and entertaining style.

2. Klein Organic Chemistry

Coming up second right after Clayden, its Organic Chemistry by David R. Klein. From a purely introductory organic chemistry textbook point of view, Klein Organic Chemistry might come up slightly above Clayden Organic Chemistry.

Clayden’s is our top 1 option because it is versatile to cover different needs or situations. But if you are interested on the best organic chemistry textbook to follow and understand introductory organic chemistry concepts, Klein is the way to go. It is also on the affordable range of textbooks.

Klein Organic Chemistry Standalone Book uses a skills-based approach. They introduce and build on top of all the typical concepts that you can find in any organic chemistry textbook. But they emphasize on the developments of skill to understand and support these concepts. Many professors I know believe that this book follows the best approach to teaching organic chemistry.

Klein: An excellent tool for students looking for the best introduction to organic chemistry

The book includes many problems, not only at the end of each chapter (the traditional manner), but also wherever they might be relevant for the reader to understand the content. If you are really intro problems, you might also want to grab a copy of the student study guide and solutions manual.

This organic chemistry textbook includes many colored diagrams, which especially useful to identify different kinds of bonds, or to illustrate distribution of charges.

Overall, Klein Organic Chemistry is the best organic chemistry textbook for getting the foundations of organic chemistry right.

3. Organic Chemistry as Second Language

David R. Klein is not only author of the standalone book that we ranked as the best organic chemistry textbook, but also has published Organic Chemistry as Second Language. I found that many people confuse both of them, but they are two completely different books. Klein Organic Chemistry Standalone s a classical 1300-pages-long textbook which covers beautifully all organic chemistry concepts that you will need.

So what is the big deal with this other book?

Well, on the other hand, Organic Chemistry as Second Language is like a 400-page condensed version of the longer book. This version mainly omits backstories, unnecessary examples and case studies. It boils it down to what really is important tot understand organic chemistry: concepts, concise introductions, clear explanations, examples and problems.

Organic chemistry is not an easy subject. If you are a student who is going to start taking organic chemistry courses, you need to be prepared. We would say that Organic Chemistry as Second Language is the best organic chemistry book for getting ready to this subject.

If you are just interested in acing organic chemistry, this book is definitely your best weapon. But this does not mean that that this book is just for that. No, it definitely covers everything most other textbooks do, but just in a much more concise and practical way. Furthermore, this book includes all the problem solutions by itself, so there is no need to purchase a separate solutions book.

Should I go for this shorter option?

But it is a rather unusual chemistry textbook, as it is not the typical full book with over 1000 pages. Considering that, we will try to help you decide if Organic Chemistry as Second Language is right for you.

You should buy Organic Chemistry as Second Language if:

• You are looking for a book that you can actually read entirely the month before starting your organic chemistry course, and go from the very bottom right to the top in terms of preparation.
• You are a bit desperate and think that organic chemistry is too difficult for you. This book will get you out of this.
• You want to ace organic chemistry courses/exams (which is absolutely not mutually exclusive with it being an awesome tool for learning!).
• You want the perfect complement to other regular organic chemistry textbook, or to a course in which they give you decent sets of materials.
• You are a professor who wants to put together an efficient, effective and complete organic chemistry course.

You should not choose Organic Chemistry as Second Language if:

• You are already familiar and understand properly most introductory organic chemistry concepts.
• You want to buy a book to go deep into more advanced concepts.
• You want a good organic chemistry reference textbook.

Overall, this book is great for grasping the basics of organic chemistry. It gets you in the best possible shape to learn and ace organic chemistry.

4. Advanced Organic Chemistry

Ladies and gentlemen I present you the best organic chemistry textbook for advanced users. Carey and Sundberg Advanced Organic Chemistry is actually a pair of two textbooks (Part A and Part B), which complement each other very well, but they are completely independent in terms of contents.

This two-part book is my absolutely favorite in the chemistry section of my shelf. I own both the third and fifth edition of the series, and it has been updated significantly to account for the most recent advances in research.

Advanced Organic Chemistry is simply the most brilliant and detailed account in the field of organic chemistry. Throughout the two volumes, all concepts are thoroughly explained, with many examples organized in schemes that resemble a real scientific review article. This pair of books is probably not the way for absolute beginners taking their first organic chemistry course (it would still work, but a lot of information will be over your head). However, if you are an intermediate undergraduate to a graduate student, this textbook is must have! Check out each one of the volumes below:

Advanced Organic Chemistry Part A: Structure and Mechanisms

The first part deeply covers the fundamentals of organic chemistry, and basic types of mechanisms. This is a stand-alone top-tier book on these topics, but it is very well complemented by the second volume, which deals with reactivity and synthesis.

Advanced Organic Chemistry Part B: Reaction and Synthesis

Part B of the absolutely best advanced organic chemistry textbook focuses on types of reactions and their applications in organic synthesis. The two books together give the most comprehensive foundation on the study of organic chemistry that you can find.

I still have to meet an organic chemistry professional that doesn’t own or hasn’t heard of Advanced Organic Chemistry as the best organic chemistry textbook.

5. An Introduction to General, Organic and Biological Chemistry

We are jumping now from the most advanced organic chemistry textbook to the most general one. Timberlake’s Chemistry is closer to a general chemistry textbook which then moves further into both organic chemistry and biological chemistry.

Are you getting started on your journey to learn chemistry and you are interested in a more organic-focused book? This is definitely your answer!

You don’t really need the typical general chemistry book before you dive into Timberlake. You can start from literally zero chemistry knowledge. The book starts with the mandatory math behind chemistry, and glues everything together amazingly.

It holds A LOT of content on it, but it doesn’t make it difficult to read. There are great examples, study checks and practice problems throughout all levels of “chemical specialization”.

This book can get you through any general chemistry course, and any introductory organic chemistry or even biological chemistry courses. Besides, if you are interested in learning chemistry by yourself, from general concepts into organic chemistry, this is most likely the best way up.

6. Bruice Organic Chemistry

Organic Chemistry by Paula Y. Bruice is one of the most recently updated textbooks out there. If you want to put your hands into an organic chemistry textbook that is extremely well written and easy to follow, Bruice should be on your top list.

This book focuses on answering “why” questions continuously, so it is constantly solidifying and re-solidifying the concepts after they were already introduced. There is a lot of practice questions that you can dig into.

One of the strongest point is the way the book redirects you all the time to where the concepts were first discussed. In this, way, if something is not really clear, you can instantly find what you need to read to understand it. This way of focusing on concepts, and further building in top of them, brigs up Bruice right behind the 5 best books for organic chemistry.

7. Vollhardt Organic Chemistry: Structure and Function

This is one of the most famous textbooks for organic chemistry, Peter C. Vollhardt is a great educator. It presents all the concepts and the subject comprehensively. Vollhardt will not only give you the basics, butt it will dive deeper into concepts, reaction mechanisms, and explaining what exactly is happening in all types of organic reactions. This a very complete book that will never be out of fashion.

Probably the most significant downside of this organic chemistry text is that it is usually expensive. But if you can afford it, by all means, go for it!

I would highlight how systematic the book is, and this is really good for beginners. They stick to the IUPAC nomenclature in all cases. For example, they use “propanone” instead of the common name “acetone”, or “oxacyclopropane” instead of the common “ethylene oxide”. Sometimes common names that go out of systematic notations can confuse students. You won’t have this problem with Vollhardt’s book.

Apart from that, this book is one of the ones that have the most amount of material, you might find it dense sometimes, but it makes a perfect reference organic chemistry textbook.

8. McMurry Organic Chemistry

John McMurry is another great organic chemistry textbook, recommended by many professors. I have an old first version of this book, and as it progressed forward through the years it has become significantly thicker, therefore covering a wider range of topics. However, some people claim that it actually got worse on the re-editing process. I haven’t compared different editions myself, but it is something to account for.

If we were to compare it to its direct competitor, Vollhardt, I would say that Vollhardt excels in amount and variety of content. On the other hand, McMurry is much more concise, resulting in clearer explanations. McMurry is very easy to read, and will make you fall in love with organic chemistry! It is also a more affordable option.

The main downsides that I find in this book are the lack of enough practice exercises of increasing difficulty, and tips for further tackle more difficult problems. Apart from that, McMurry’s is a perfectly fine organic chemistry textbook.

9. Wade Organic Chemistry

The 9^th edition of this book has been published recently (2016) and it was authored by Leroy G. Wade and Jan W. Simek. It is a brilliant piece of educational material, and definitely stands within the top organic chemistry textbooks.

The book focuses greatly on homework problems, and update them with every new edition. In terms of contents, it is great, and it is updated fairly often.

The downside with Wade is that, for a 2016-last-published book, lacks a lot in the graphical design and formatting. The schemes and drawings are not very appealing and sometimes can be difficult to visualize, which is harmful while learning organic chemistry.

But on the other hand, explanations and practice problems are just great. Besides, Clayden’s, Wade’s was the organic chemistry textbook that I used myself during my undergraduate days. But I think by know you already know which one I prefer.

10. Solomons Organic Chemistry

Another classical organic chemistry textbook that definitely makes it into the top 10. Ranking it last doesn’t mean that is not good. It’s a nice text. It explains all the concepts fairly well, and it feeds the importance of understanding and not just memorizing. It is pushes you through the logic of organic chemistry, and makes good uses of analogies. You can check out Solomons Organic Chemistry here:

The order in which the contents are presented is kind of weird. Sometimes it feels like you have to read though the latest chapters to understand the first ones. That is not the biggest problem ever when it comes to a college textbook, but problems such as this prevent it from being the best organic chemistry textbook.

Complementary and Miscellaneous Materials

After an exhaustive review of the “classical” best books for organic chemistry, we wanted to mention three more books that may be interesting to you. If you are looking for complements to your organic chemistry textbook for self study, you might want to look at some of those.

You have decided which textbook to purchase, but you are hungry for more, to get really well prepared, or maybe a book for self study!

These are not the typical “standalone” college textbooks. However, the highly practical and instructive approach of these books may be appealing for you. They definitely will help you establish the bases of your learning. Then you can build on top of that.

11. The Organic Chem Lab Survival Manual: A Student’s Guide to Techniques

This is the best organic chemistry book for the laboratory. The chemistry lab books could fill an entire post with reviews by itself. But I wanted to make sure to add here the best one, as a complement of any actual textbook that you might have chosen.

This survival guide is the best companion for the typical university-level (sophomore-junior) organic chemistry lab courses. If you are either teaching or taking any of those courses, get a copy of this book and jump into the next level!

I have to admit that I didn’t know this book until quite recently, but when I read it I thought I would have made my life through school incredibly easier! It covers lab safety, how to properly keep a lab notebook, basic equipment, organic chemistry lab techniques (such as recrystallization, extraction, distillation..) lab tricks, basic experiments,  chromatographic techniques such as TLC or flash column, and finally spectroscopic and other characterization techniques. Basically everything you need to survive though any organic chemistry lab that you can find out there. The book is very useful and extremely engaging, with a playful/informal writing style, you can even find some jokes on it. You wont regret this purchase!

12. Arrow-Pushing in Organic Chemistry: An Easy Approach to Understanding Reaction Mechanisms

I think this is one of the best complementary books for organic chemistry. This book by Daniel E. Levy fills a significant gap in chemistry undergraduate education, organic chemistry is all about arrow pushing. I believe that most professors and students would benefit significantly of reading through Arrow-Pushing in Organic Chemistry. The book draws a nice picture of how you should approach learning arrow pushing mechanisms, which is basically the language of organic chemistry.

It is a great workbook or complement indeed. However, this is not a textbook or a purely instructional book. It doesn’t start off from the beginner concepts, it doesn’t explain the basics of organic chemistry in the first chapters. It literally dives into arrow-pushing mechanisms, so it is a highly practical resource. It does start explaining concepts after several chapters, and goes back to explaining things that were already approached at the beginning in a practical manner. It follows a weird order, but it might work for you if you just want to “see stuff working” from the start of your read.

13. Organic Chemistry I for Dummies

This member of the “for dummies” series is an interesting quick overview of an introductory organic chemistry course. This is not a textbook, and should not be treated like so. With Organic Chemistry I for Dummies you can scratch the surface of organic chemistry in a very practical manner. I’m not a particular fan of this text book. Not because is not good for learning: it is great for learning the very basics, but after you will run out of resources.

It covers concepts such as nomenclature, stereochemistry, functional groups, very basic organic chemistry reactions (eliminations, substitutions), and has some nice problems. Everything in a very informal and straight-to-the-point fashion. If you are taking an introductory organic chemistry course, this might be the perfect complement. It is very visual, which exactly what organic chemistry asks for. Since it is not a complete textbook, just an introductory practical summary, it is a very affordable resource.

After soon you will be hungry for more, so that is why I put this book on this last complementary section.

Wrapping Up: Quick Summary of Our Top 3 Picks

So I will close with a quick reference: The three top organic chemistry books. One of these will work for you in most situations, they are safe bets. Depending on your specific needs, you can choose one or another:

Perhaps you are not quite into organich chemistry yet. If you are preparing your AP chemistry exam, you should take a look to this review of our top recommendations to crack the AP chemistry exam! Also, here’s for the SAT chemistry exams.

We have also reviewed some chemistry sets for young students (or even for adults!).

Furthermore, by popular demand after getting several emails, we have also arranged some other review guides:

• If you are just getting started in chemistry, check out the best general chemistry textbooks out there!
• A review guide for helping you choose the best inorganic chemistry textbook!
• Or check out our general guide for learning chemistry. Plenty of resources and recommendations over there.

If you miss any organic chemistry books that you are interested in, let us know in the comments and we will definitely get our hands in one copy and add it to the review. Enjoy learning organic chemistry and good luck!

The post The Best Organic Chemistry Textbook [A Definitive Guide] appeared first on Chemistry Hall.

Chemistry is an experimental science, and the best way to enjoy it and learn about it is performing experiments. No matter if you are a hobby chemist or a parent that wants to enjoy learning about chemistry with your kids.

There are countless chemistry experiments for kids that can be educational and safe. On this matter, make sure to check out some already assembled chemistry kits for kids (and adults!)

Doing experiments goes a long way for inspiring kids to get interested in science!

Maybe you are just a science enthusiast. In any case, this guide is certainly for you, we have the best recommendations for setting up a home chemistry lab.

We have a huge selection of materials listed and described in this review, but if you want to skip right through it and just check out my best recommendation, you can just check out this set of glassware:

Keep reading if you want something more specific. This is basically what we will cover in this post:

Introduction: Can You Really Do Chemisty Experiments at Home?

I have been working on a professional level lab for several years. But my passion for chemistry started by just doing chemistry experiments at home. Mixing salt and water in plastic beakers that I found sitting around my house. My love for chemistry evolved over time, and I got my hands on a good collection of glassware and chemicals, mostly ordered online. This is probably the simplest way to set up a home chemistry lab easily and cheaply.

When I was just getting started, (before taking university level chemistry courses), I was overwhelmed by the possibilities. Now, ten years later, I decided to put together this guide. This will be as close as possible to what I would have loved to read when my interest in chemistry started to grow.

Disclaimer: This is not intended nor will disclose any information regarding the preparation or manipulation of illegal/dangerous substances. Relevant safety considerations will be pointed out throughout the guide.

Safety First: Basic Personal Protective Equipment (PPE)

No dangerous experiments will be described on this guide, but the use of basic PPE should come as natural as breathing when working in chemistry. Even I, a professional chemist, wear my safety glasses all the time even when performing the most trivial tasks in the laboratory (even just sitting around talking with a colleague).

You do not really need anything fancy, some goggles such as these will work perfectly to keep your eyes safe:

Besides from safety glasses, it is always good to have at hand some protective gloves. Any kind of nitrile or latex cleaning gloves in the supermarket will fit the purpose of handling most chemical substances that you will use doing chemistry experiments at home. I am not going to lie, a lab coat might seem like overkill in many cases, especially if you are just performing chemistry experiments for kids, but it is always handy to prevent things to spill and ruin your clothes. It does not have to be anything expensive to fit this purpose.

Keep Record of your Chemistry Experiments in a Lab Notebook

This is the cornerstone of scientific research and experimentation, making notes about observations. Plan clearly beforehand what you are going to do, write down the “recipe” of what you “mixed together”, record what happened, when and how. Then try to rationalize why it happened afterwards, and write it down. As simple an observation or a way to add an “ingredient” as it may seem, I can assure you will not remember it properly in a few days. It happens to the best of us. For this purpose, any lab notebook will work, as long as it is resistant. You can browse some examples in the pictures below, or just visit our post about choosing the best lab notebook.

Defining the Space for your Home Chemistry Lab Set Up

Even if the materials you use for your chemistry experiments are not very harmful, it is a good practice to clearly define a working area in your house. If you live in a small flat, any table as far from where you keep your edibles would do. I used to use my bathroom when I was a kid (it was my only option), but if you have a ventilated garage, a shed, or even better, an outdoors zone, that would be a great place. You usually want a source of tap water and electricity close-by. Try to keep it to that working zone, or “lab bench”, it will not only be safer, but it will make it easier to handle everything.

Essential Equipment for a Home Chemistry Lab

So you are almost ready and cannot wait to set up your first chemistry experiment at home. What do you need? Of course, you need lab equipment. Specifically, glassware and plasticware are the usual options. Borosilicate glass is better because it allows heating, and in most cases it will be easier to clean and last longer in good shape. As long as you don’t break it!

If you really want to take this seriously and you want to make your life easy, here is your perfect solution. Get your hands in a bit of everything you need. A starting chemistry glassware set will set you on track. Out of the ones that I found online this seems to be the best for the purposes of setting up a lab for doing chemistry experiments at home, just click below to see more details and grab your own chemistry set:

This set gathers essential items. Beakers, Erlenmeyer flasks, volumetric cylinders, glass bottles, test tubes (and its racks), stoppers, a metal clamp to heat things up, a glass rod for stirring mixtures, glass pipettes and some other things. This is basically everything that someone wanting to set up a home chemistry lab needs to begin with, so it is my first recommendation and a safe bet.

But maybe you want to buy some specific things. So here are my basic recommendations for doing chemistry experiments at home.

The Most Basic Chemistry Glassware

Before starting: Keep in mind that you can always take a look at our guide of chemistry flasks if you notice something missing, or if you want to identify a piece of glassware that is sitting around in your garage.

The first must have: beakers. Glass beakers are the bread and butter for doing chemistry experiments at home, extremely multipurpose. Check out the set below if you are interested:

Coming up second, the Erlenmeyer flask. Just like beakers, but can be better for specific situations, for example, for shaking mixtures without spilling. Get your hands on some Erlenmeyer flasks, it is an absolutely essential item in any home chemistry lab.

The Best Accessories for a Home Chemistry Lab

It is always extremely handy to have a metal support stand, and especially with some clamps attached to it. These are multipurpose and once you get used to them you will not be able to live without one. Basically it allows holding flasks while you work with them. This is an example of a support with clamps and retort rings:

While not so common to test reactivity in professional set ups, one of the best things to have a round in a home chemistry lab is a plastic rack with some glass test tubes, with its corresponding rubber cap. This is the absolutely best way of, as its own name says, test things! Just toss reagents in the tube, add a solvent and shake it. The rubber stoppers will prevent contamination, and allow shaking without spilling a drop (always be aware of possible overpressure building when working with closed systems, though!).

And this pretty much summarizes the basic requirements. Of course the possibilities on equipment are endless, and as you progress on your home chemistry experiments, you may want to purchase more advanced or specific equipment. See the appropriate section below to explore the next level.

Gathering Basic Chemicals for your Home Lab

I will start with an honor mention: my favorite “home-level” chemical for doing fun experiments, copper sulfate (CuSO₄). This beautiful blue solid is not harmful, and is usually employed as algae control agent in swimming pools. But the nice thing about it is the beautiful crystals that you can make with it:

They look beautiful, don’t they? Well, keep reading, I will share with you a procedure to make them in the “your first chemistry experiment at home” section. Get your hands on some of copper sulfate:

Now that I got my baby blue out of my chest, let’s talk about typical chemicals that you can obtain in supermarkets, grocery stores or hardware stores.

The Most Basic Chemicals in a Home Lab

• Distilled water. Regular tap water will work for most chemistry experiments performed at home, but you can easily get your hands in a bottle of distilled water in hardware stores.
• Organic solvents. Such as acetone (great for cleaning up glassware, we spend gallons of it every day in our lab), or toluene mixtures (paint thinners) can be also accessed through hardware stores. Also alcohol (ethanol or isopropanol) of decent purity can be acquired in any pharmacy or most supermarkets.
• Common acids such as hydrochloric acid, can be bought in supermarkets, and are extremely common reagents. If concentrated, they should be handled with special care, always wearing safety glasses and gloves. If you get a spill with an acid (or a base, for that matter), rinse with plenty of water and if it hurts or stings, don’t hesitate to go see a health professional.

Another very common chemical is sodium hydroxide. You can buy water solutions, but in my opinion is easier to just buy it as a pure solid (NaOH) and dissolve the amount you need. This reagent has plenty of home applications, besides doing experiments for fun or educational purposes: Sodium hydroxide, or lye, can be used to unclog drains, or even better, to make you own soap.

Useful Household Chemicals

Your usual best bet is looking for household chemicals. To list some more:

• NaCl (sodium chloride), also known as table salt. It also works for growing crystals, but not as pretty as the ones made with copper sulphate.
• Borax, or sodium borate, can be found in many department stores.
• Vinegar: It is actually an aqueous solution of acetic acid. White is probably purer.
• NaHCO₃ (sodium bicarbonate), or baking soda, is a very mild base. It reacts with acetic acid on vinegar, and a typical chemistry experiment for kids is making a volcano with baking soda and vinegar.

The list could go on forever. We will list the specific reagents that you will need, and how to find them, in each post about doing chemistry experiments at home.

How to Properly Store your Chemicals

You need appropriate containers to store your reagents. This prevents any contamination, which can go either way (contaminate your precious chemicals or contaminate yourself with them). In terms of storage of solid chemicals, or small amounts of liquids I recommend you to get some screw-cap glass vials:

To store large quantities of liquids, glass storage bottles are a must:

Make sure to get a good permanent marker, or a set of labels, so you can always label every container and make sure what is inside, or how much.

More Advanced Equipment and Set-Ups

Two of the most basic operations in a chemistry laboratory are flitration and ditillation.

Filtration is separating a solid from the liquid that it is suspended on. You can get away with a regular coffee filter and filtering paper, but if you really want to go pro-mode, this filtration kit, with your own vacuum pump, provides everything you need for a very reasonable price:

The most famous operation or experiment in a chemistry lab is a distillation. A distillation is basically the process of separating mixtures of liquids with different boiling points, or level of volatility. This is a extremely educational experiment for kids, and has found many applications in home chemistry labs, such as distillation of essential oils. There is so much that you can do with a distillation kit that I will revisit this experiment in a future post. In the meantime, you can get your hands in a proper distillation, which is not particularly expensive. Of course, to hold it up, you will probably want to have also a support and clamps (see the basic section above).

Gearing Up to the Next Level

A stirring plate with magnetic stirring bars is literally something that you use every day in a professional chemistry laboratory. Although you can get away with a glass stirring rod, the joy of automatic stirring is difficult to overcome, especially if you want to run a chemical reaction at home that takes a significant amount of time to complete (some chemical reactions are virtually instantaneous, but others can take several hours, or even days!). Apparently, small stirring plates are not particularly expensive.

Furthermore, you probably also want to have some extra magnetic stirring bars around, like that you can stir different containers using the same plate.

This is how stirring plates work:

Accurate Weighing your Chemicals

Finally, a balance that allows you to weight your reactants for your chemistry experiments comes in very handy. You don’t need to go for a super precise professional analytical balance. Any food balance will do, just don’t mix it up with your actual balance for food in the kitchen… You can grab some cheap kitchen balances here:

I will close this section now, though I could really go on forever. I will revisit home chemistry equipment in the future, probably in each post about specific home chemistry experiments in which I will mention what material you are going to require.

Your First Chemistry Experiment at Home

You are almost ready to start having fun. I promised before a nice experiment to start with. One beautiful thing that you can do in chemistry is growing crystals. Some compounds, especially inorganic salts, tend to be able to crystallize easily, and you don’t need a huge set of glassware. Just one or two beakers, a piece of cardboard, some strand to hold the seed crystals, and of course, the material you are going to crystallize. I recommend you to go for the good old copper sulfate (CuSO₄).

Copper sulfate is a nice blue solid that crystallizes very easily from saturated solutions in water. In the corresponding section I gave you the link to buy copper sulfate and some beakers. You would be all set with that!

There are plenty of visual guides online about the procedure that you must follow, so check out the following video:

Where do I Go Now? Further Reading and Final Remarks

If you purchased some of the material discussed on this post, you will be ready to carry out many chemistry experiments at your own home! Stay tuned for more content on specific experiments, but you can go ahead a check some experiments in chemistry textbooks. I strongly recommend Illustrated Guide to Home Chemistry Experiments: All Lab, No Lecture, by R. B. Thompson. It’s been on my shelf since it was published 10 years ago, and I absorved it from cover to cover. Take a look at it below!

Another cool technique that you might want to introduce at your home lab is thin layer chromatography, so feel free to check this other guide.

Feel free to ask for any further orientation that you need, or information about any experiment in the comments. Best of look and good chemistry!

The post Chemistry Experiments at Home: Setting Up a Home Lab appeared first on Chemistry Hall.

Confirming the actual structure of a molecule, is still a big challenge now-a-days. The advances in techniques such as NMR (Nuclear Magnetic Resonance) spectroscopy, or single-crystal X-ray diffraction have significantly helped speeding up this problem.

Molecular structure determination

Every month we get reports of chemical structures whose structures have to be reassigned or revised after some study (either synthetic or just based on characterization techniques) is carried out. On this regard, it is worth remarking the difference between scientific models and reality.

Truth is, even today, the methods for the characterization of molecules available to use routinely (which are explained in the most basic chemical bibliography), can be consider rather rudimentary, and of difficult interpretation for non-experts. Let me be honest, I am a trained PhD organic chemist and if I had to take a look at the NMR spectra of a complex natural product such as maitotoxin, I would probably have no clue what I am looking at.

Single crystal X-ray diffraction is probably the closest method to easily visualize the structure of a molecule in 3D. However, this is not a bulletproof method. The sample preparation (growing single crystals) required for this indirect technique, renders it useless for a wide variety of chemical compounds.

Can we actually see real molecules or atoms?

Accordingly, I would say that by today, there should already be a method that allows taking a direct microscopic “picture” of any compound you like, and immediately visualizing its structure in a screen. Apparently we are not quite there yet (in regards to “any compound”, keep reading). However, the answer may come under the name of atomic microscopy, and all of its variations.

Atomic force microscopy (AFM) or scanning force microscopy (SFM) is a very high resolution probe-microscopy technique. It allows us to actually “see” or “take real pictures” at the nanometer-scale, in which the molecular realm lies. A picture is worth 1000 words. In the example below, scientists make use of this technique to get pictures of a compound called naphthalenetetracarboxylic diimide. We can actually see a real molecule.

Much more recently, researchers at Oxford and IBM used STM-AFM to generate and visualize in situ the first cyclic allotrope of carbon, cyclo[18]carbon.

Seeing atoms in motion

The world of visualizing at the atomic level took a leap more than ten years ago. In 2008, a research group reported the imaging for the first time of light atoms and molecules on graphene. Subsequently, the same team managed to observe for the first time the actual movement of insolated graphene atoms in real time. The following movie from the Berkeley team shows the growth of a hole in a graphene sheet. For this experiment, a beam of electrons is focused to a specific spot on the graphene sheet, blowing out the focused carbon atoms making a hole. Besides, it can also be observed how the carbon atoms rearrange themselves (edge reconstruction) to adapt a more stable configuration.

The Boy And His Atom: The World’s Smallest Movie

The Guinness World Record for the “Smallest Stop-Motion Film” is held by a movie recorded by IBM scientists. Sometimes, nanophysicists also need to have a bit of fun, and what they decided is to “film” a movie by using scanning tunneling microscopy, a the result is in the following video:

By the use of this technique, the scientists managed to move a lot of molecules of carbon dioxide following their will. The result is a movie you can only see using a microscope that magnifies one hundred million times.

Direct observation of chemical reactions

Obviously, taking real pictures of molecules and atoms was just not enough for the scientific community. If we fast-forward to year 2013, atomic microscopy, more specifically, non-contact atomic force microscopy, allowed the direct imaging of molecular structures during a chemical reaction. Some results of these experiments published in the journal Science are displayed below. We cannot only see actual atoms molecules, we can observe directly chemical reactions!

AFM in structural determination

This field started as a cluster of isolated cases, but as the years went by, more and more examples of the application of this set of physical techniques are being constantly reported. The level at which the studied molecules can be observed is rather impressive. A recent example is the actual structural determination of a natural compound, breitfussin A. Several functional groups of the molecule were derived from classical spectroscopic data (a). Then, an AFM image (c) allowed observing the real structure of the molecule, placing each piece of the puzzle (a) in the correct spot. This established the previously unknown structure of the molecule (b).

Taking real pictures of complex chemical reactions

On the reactivity side of things, much more recently, it was possible to directly image the course of a reaction called the Bergman cyclization. This is one of the most fascinating rearrangements in chemistry. The chemical transformation is directly induced in the metal surface in which the atomic microscopy procedure is carried out.

However, as stated at the end of the introduction, not every molecule or reaction can be a candidate for a STM study as these. Several conditions need to be met. One of them (which might have already called your attention) is that the analyzed compounds need to be near-planar. These techniques rely on depositing the molecules of the compound in a planar metal surface, so planar molecules are the ones that give more interpretable data.

The search for the “Holy Grail” of structural determination

To finish this short essay that does not make justice to the whole field of molecular imaging, a recent application of what is called micro-electron diffraction (MicroED) will be discussed. This brilliant application of electron diffraction, allows overcoming probably the biggest problem on classical X-ray diffraction methods: the requirement of crystalline material of the molecule which structure wants to be elucidated.

This technique allows taking simple powder of any non-crystalline solid, without almost any sample preparation, and getting 3D structures of the powder nano-crystals in a matter of minutes, with extremely high resolutions. The structure of molecules with very high complexity, as thiostrepton, could be obtained unequivocally.

Is this the future of chemistry?

Can we see real atoms and molecules at this point? I would say that we definitely can. All the results that have been described in this article were published only over the last decade. Atomic microscopy seems to be here to stay, and it might be one of the tools that finally allows chemists to stop relying in rudimentary techniques for the determination of molecular structures. Only time will tell.

Stay tuned for more posts about the future of chemistry, share, and post your thoughts in the comment section!

The post Can We See Real Atoms and Molecules? Electron Microscopy at a Glance appeared first on Chemistry Hall.

1. Lab hacks for taking care of air sensitive chemicals: What works and what does not

I have seen people remove the “sureseal” from Aldrich bottles of buthyllithum and exchange it for a rubber septum. This is not the way to go: a piece of rubber full of holes is not protecting you reagent at all. The only long-term reliable method for protecting air-sensitive commercial compounds like BuLi is the metal/plastic seal that originally comes attached to the bottle. Aldrich’s sureseals worked fine in my experience, if you want something more, Acros multi-layer seals provide an even better reliability.

A more useful lab hack is to use a needle that leaves almost no hole while using it to take the reagent out of your bottle. A good choice is using 4 in. 22 ga needles (Fisher #14-817-102). I found them for the first time in my current lab and they work perfectly fine.

But if you really need to store a chemical properly under complete inert conditions you should transfer it into a Schlenk bomb.To do so you can just follow the same procedure than doing a cannula transfer, having throughouly purged it with an inert gas like Ar beforehand. Of course, most of this reagents can be titrated so you can know its exact concentration before using it, which is required especially in cases where you do not want to use an excess but a stoichiometric amount of the compound. Shenvi’s group in Scripps has published online a very nice guide on titration of common soluble RM, R₂NM and ROM reagents.

2. Most commonly used pyrophoric reagents

Most of the fires and explosions that can happen in the labs are usually caused by the same chemicals. We found very interesting to share a list of the most common reagents that might cause a fire or an explosion if not handled properly.

The most popular one would be sodium metal, which is still used in many labs as drying reagent for solvents via distillation. Take special care when handling it under air atmosphere.

Lithium aluminum hydride (LiAlH₄) is a frequently used reagent for performing reductions. It is of extreme importance to add the hydride in very small portions to the substrate, and in a ice/water bath if possible, especially at the beginning of the addition. Another approach would be to add a solution of the substrate to a suspension of LiAlH₄, once again, in a controlled manner.

Palladium on carbon (Pd/C) can also ignite in contact with MeOH (a common solvent for hydrogenations), so it is usually recommended to cover completely the Pd/C with another solvent like toluene, and then add the substrate and the methanol. Obviously, hydrogen can also cause explosions, so if you are planning to do hydrogenations, consider asking for advice or training first. As a general rule, set up the reaction completely under Ar/N₂ atmosphere, only exchange for H₂ last. When the reaction is complete, exchange again H₂ for inert gas and then you can open the flask.

Other common chemicals that may ignite are organolithium reagents, especially tBuLi. Always quench the syringe you used for the addition with not dry Et₂O or THF, you do not want to create a flamethrower!

You can check some guidelines on the safe use of pyrophoric reagents by Columbia University.

3. Short but very useful advices, lab hacks and proverbs

• Labelling a compound takes 5-10 seconds. Identifying an unlabeled compound may take 30 minutes later (if you are lucky).
• A bit of an impurity can make a huge difference in color. If a product that should be colorless looks orange, brown or whatever, do not assume your reaction failed.
• If you do not have time to do something properly/right, make sure you do have time to do it again.
• There is no “having too much starting material”.
• Hofstadter’s law: Everything will take longer time than you think, even if you take into account this rule.
• A week in SciFinder will save months in the lab.
• One gram in hand is worth two in the reaction flask.
• Garbage in, garbage out.
• You get luckier the more you try.

You can find more of them, as well as loads of advice and lab hacks for working in the lab at NotVoodooX (University of Rochester)
This is a really neat website, especially for beginners. I would recommend everyone to have a look at it.

These are general tips that will be useful mainly in professional labs, but you might find something useful even if you just want to do chemistry experiments at home!

4. Plan the project before planning the experiments

Collecting data that will not be publishable is not an efficient way to organize your work. You do not want to end up with a lot of meaningless or unconnected data after weeks or months of work, this just would be a disaster.

The best idea is to always keep in mind the big picture. What do you actually want? Even if the next experiment that you have in mind looks cool, if it does not provide any meaningful insight to the whole project, it is not worth performing. But if it gives you a bit of knowledge about how your reaction works, or puts you in a closer position to your goal, go for it.

5. Lab tricks for weighing compounds

Over the years I have seen people use a lot of different tricks or lab hacks to weigh chemicals. Here I list some of them that can make your life easier every day in the lab.

• If you are weighing a compound from a small container (let’s say, a 5 mg bottle of catalyst), you can just put the container in the balance, set it to 0.0, and then pick with your spatula until the balance reads the negative value of the amount you wanted to measure. I find this very useful when I am setting up several small-scale parallel reactions with the same reagents but different conditions.
• If you need to weigh amounts bellow the accuracy limit of your balance, just weigh a larger amount, dissolve it in a known amount of your reaction solvent, and add the corresponding volume of the resulting solution.

  

• When I find myself with the need of weighing oils/liquids which I do not know the density of, the best solution is to weigh the appropriate empty syringe, then fill it with my reagent and weigh it again. Just adjust until you have picked up the amount you needed. Of course now with the values of weigh and volume you can calculate the density of your product for the next time.
• For very tiny amount of liquids, apply the first point: Weigh the oil container, set the balance to 0.0, dip the tip of a pipette, check the mass that you have taken. Then adjust picking up more amount or dropping some of it. When you have the desired mass on your pipette, rinse it in your reaction solvent and you are done.
• If you want to set up one (or more) small-scale reactions (lets say, 10 mg) but you only have some mg of your starting material (50 mg), you just need to dissolve it in your reaction solvent, for this example 5 mL, and then take 1 mL of the solution to each of your reaction flasks/vials.

6. Lab hacks for TLC

First of all, if you need help on anything related to TLC, check out our complete guide for thin layer chromatography here.

• Do you need to run a lot of TLCs in the same solvent system at the same time? Just get a big glass container that you can close, fill it with sea sand, and then your solvent system. You can now just stick all the TLC plates you want on the sand and they will run at the same time.
• Classic TLC are mandatory before doing a column or preparative TLC purification. This seems obvious, but should always be kept it in mind.

  

• A nice thing to try if you are not getting good TLCs is after spotting your reaction (and the other components/mixtures) eluting it for a few millimeters in pure MeOH. MeOH will concentrate all the spots, and you can now mark the front line and run normal TLC. This gives very nice TLCs and can solve problems like big spots, or spots overlapping.
• If you think a compound is not stable in silica, try running a 2D TLC: Use a square TLC plate and spot the sample in one corner. First run the plate in one direction, then dry it and run it turned 90 degrees (with the line of spots at the bottom). If the compounds are stable in silica, all the spots should appear on the diagonal. If any compound does not, it will probably be decomposing.

7. Dealing with air sensitive compounds NMR

If you have one, you can use a Schlenk line NMR adapter. You can insert the neck of your NMR tube in the bottom hole and do vacuum/Ar cycles. Then you can just fill your tube with your compound in dry deuterated solvent. 

If you do not have one of those adapters, you can use a small rubber septum: it has enough room to insert a needle from your Schlenk line, so you can fill the tube with an inert gas.

You can usually dry your deuterated solvents like CDCl₃ passing them through a plug of activated alumina (A pipette with a cotton plug will work. This will also remove acid traces from chloroform), or adding 4A molecular sieves. You can also try adding some CaH₂ or K₂CO₃ and the filtering them out. If you have access to a glovebox and closed-ampoules of deuterated solvents, you can totally skip the drying step.

8. Organizing your fumehood

• Do you use a certain solvent or bench reagent a lot of times? Instead of wasting every time a new syringe and needle, what I do is sticking some column test tubes in the walls of my fumehood, label them, and put in there a syringe+needle which I use to manipulate a certain solvent or reagent. For example, I have one fo

  

  r my deuterated chloroform, another one for the HPLC grade solvent that I use every day for setting up my reactions and another one for the stock solution of my internal standard to calculate NMR or GC yields.
• Fill and label washing bottles with the technical grade solvents that you use normally.
• If you use reflux condensers in a daily basis, it is probably better if you leave them all permanently connected in series to your cooling water and clamped in the back of your fumehood.

Besides, organizing your lab notebook is just as important!

9. Hacks for pulling solvent off your samples

Sometimes you have a new product, and after checking out your NMR for characterizing it, you find that a lot of solvent shows on the spectra. If you are having a hard time removing the solvent from a sample, there are several things you can try. Place your container (if its hygroscopic or air sensitive, under an inert gas) intro a dry ice or acetone (cryocooled) bath for 30 seconds. Then take it out of the bath and apply high vacuum. Repeat twice more and most solvents will have left.

Another trick that I usually apply, for example right after a column purification, is redisolving my pure product in the solvent (not the deuterated one, of course) I will be getting my NMR with (which is usually chloroform) and then removing it under reduced pressure. This usually helps a lot, since the main traces of solvent will only cause your NMR solvent peak to increase a bit (most of the other solvents will be gone), but you will get a very clean spectra.

10. Miscellaneous lab hacks and tricks

• Multiple rinses using smaller amounts of solvents are better than only one with a large amount, e., 3x1mL is better than 1x3mL.
• If you want to weigh a liquid with very low boiling point, leave it in the fridge or freezer for some minutes before proceeding to do so.
• Rinse your extraction funnel with brine before doing your actual brine wash to the organic phase. It helps removing aqueous residue which remains on the separatory funnel.
• Using a short sentence to describe the result of every reaction (like “the reaction worked well”, “very clean reaction/TLC”, “only SM on GC/TLC”). Writing it down on your notebook is very useful.
• Repeat every new reaction with a positive result. Always make sure that the procedures that you create are reproducible.
• If two pieces are stuck together by a ground glass joint, try heating them up with a burner or other heat source, then it will be easier to separate them.
• If you deal with chemicals that will stick to your gloves a lot (like iodine) you can just double glove. When the moment to manipulate it comes, use the sticky reagent then throw the outer pair of gloves and you will not have to deal with sweaty hands to put new gloves on.

That is all for today, I hope you have enjoyed it and find it useful! I want to thank, apart from the sources cited/linked above, the chemistry reddit community for providing both information and inspiration for making this post. I also wanted to thank Wikimedia for the nice pictures included.

Go check our recommendations of resources if you are looking to prepare for an organic chemistry, inorganic chemistry or, any chemistry lab in particular.

Finally, if you have any doubts or if you feel like contributing with your own tricks/pictures/examples you can do it on the comments. Or even better: contact me so I can include your tricks on a future second edition of this lab hacks post (you can contribute with your own posts if you like).

The post Lab Hacks – How to Increase your Productivity in the Lab appeared first on Chemistry Hall.