The Heart of Chemistry

Most chemistry syllabuses (at both 14 to 16, and 16 to 18 ages) tend to have a variation on the following topics:

  • Atomic structure
  • Bonding
  • Periodicity
  • Stoichiometry
  • Energetics
  • Kinetics
  • Equilibrium
  • Acids and Bases
  • Redox
  • Organic Chemistry

Within each of these clearly defined topics there will be benchmarks that outline very specific things that students must know. This is great for ensuring a level playing field and making sure that all students cover lots of content. However, for me, it misses a trick.

I believe there are a few fundamental concepts in chemistry that all students must know if they are ever going to be able to become cutting edge chemists.

I call these fundamental concepts the “Heart of Chemistry”, as without them, the rest of chemistry is unexplainable:

  1. The Atom
  2. Particles in the atom
  3. Electrostatic Forces of Attraction
  4. Entropy
  5. Conservation of Mass and Energy
  6. Bonding

I will now deal with each of these individually.

The Atom

At the heart of chemistry is the atom. Yet, they don’t really exist in their pure forms. Atoms are incredibly unstable, owing to their unpaired electrons. Given the chance, they will immediately react with other substances to form molecules and lattices. Students must be introduced to this idea as they learn about the atom. The atom is just a human construct that helps us to work out how different elements will interact. They are pieces of jigsaw that cannot work on their own (apart from  the noble gases, of course).  

Particles in the atom

For students to understand chemistry, they must know and understand the particles that make up atoms: protons; neutrons; and electrons.

Electrostatic Forces of Attraction

Students must understand the concept of electrostatic forces of attraction. They should understand early on that this involves an attraction between something that is negative and something that is positive. At this point, it would be good to bring in the idea that electrons are held in atoms by electrostatic forces of attraction between the said electrons and the protons in the nucleus. Electrostatic forces of attraction will then be an extremely useful concept for further studying in chemistry.

Entropy

A fundamental concept that I think students need to be introduced to extremely early on is the second law of thermodynamics which states that entropy can never decrease over time for an isolated system. In the case of chemistry, we treat the universe as being the isolated system. So the universe tends towards disorder. In terms of chemistry, the entropy of the universe is the sum of the entropy of a reaction and the entropy of the surroundings, demonstrated in the diagram below. In most chemical reactions, energy is released to the surroundings, making them more disorded. This makes the atoms from the reaction become more ordered since they now have less energy and are more stable. This notion that particles in reactions tend towards stability, which releases energy to make the surroundings more disordered is extremely important. I also think it’s important that students realise that entropy can be determined experimentally.

 

A diagram that shows how the entropy of the universe is the sum of the entropy of a reaction and the entropy of the surroundings. If a reaction decreases in entropy but increases the entropy of the surroundings enough, then it can still increase the entropy of the universe overall. An interesting thing to look into here is the seeming paradox of entropy on life (this Wikipedia article is a good starting point if you are interested: link)

 

The Conservation of Mass and Energy

This is very much linked to the ideas included in entropy. In the universe, matter and energy cannot be created or destroyed. The same can be said for chemical reactions. The energy and matter that goes into a reaction must ultimately come out. The only difference is its form. Atoms will rearrange. Energy will change from chemical potential to heat (or vice versa). This is crucial for students to understand.

Bonding

At its heart, chemistry is about understanding bonding. This is what makes chemists tick. Without understanding bonding, the rest of chemistry doesn’t make sense and has no value. Here, we make sense of how atoms don’t exist in the real world (or at least, they exist for extremely short amounts of time). Within bonding, I believe there are some fundamental concepts that must be taught in order for students to fully grasp what is at hand. The first is that of collision theory (typically taught in kinetics). In order for substances to undergo bonding, they must first come close enough together for electrostatic interactions to occur between the protons in one atom and the electrons in another. The next concept is how the electrostatic interactions between different atoms can lead to different types of bonding. (Note: It is important for students to grasp that categorising bonding into ionic, covalent and metallic is a generalistion that is open to exceptions but makes life easier)

Conclusion

By understanding these concepts before launching into a course, I believe students (and teachers) will gain a deeper understanding of and develop a greater love for chemistry, rather than just ticking the syllabus boxes. Indeed, I believe that a lot of the traditional units at this level are simply applications of these concepts so that we can make quicker and easier predictions about how reactions might proceed before we test them out.

A case study: energetics

Most chemistry courses will have a unit called energetics, and lots of students struggle with it each year. I believe this is because they don’t really see the point of it. Energetics, in essence, is just a tool. Once you understand what an atom is, what bonding occurs, that energy and matter must be conserved and that the universe tends towards disorder it is easy to see that energetics is just a quick and easy way of applying these concepts in the real world to real reactions. Below is my first attempt at looking at this. It is raw and far from perfect:

Topic in a typical energetics unit Fundamental concept required Explanation
Exothermic and endothermic reactions Entropy, Conservation of mass and energy, Bonding Exothermic reactions release energy. This is because bonds are formed. When bonds are formed, unpaired electrons pair up and this process releases energy. This released energy helps increase the disorder of the surroundings and the universe. The converse is true for endothermic reactions. These are useful terms to use to make life easier.
Activation energy Electrostatic forces of attraction, Conservation of mass and energy In order for a reaction to occur, the bonds in the initial reactants must be broken. Bond breaking is endothermic and requires energy. You are breaking electrostatic forces of attraction and this requires energy.
Enthalpy Entropy, Conservation of mass and energy, Bonding Enthalpy is a measure of energy per mole. If you understand that bonds are electrostatic forces of attraction, you can understand that energy must be required to break them. The energy required to break a mole of bonds is a form of enthalpy.
Enthalpy cycles Entropy, Conservation of mass and energy, Bonding These include techniques like Hess’s Law and Born-Haber cycles. If you understand that energy must taken in and given out during a chemical reaction and that overall, energy must be conserved in the universe, you can understand that mathematics can be used to work out the enthalpy changes that occur in a reaction.

 

How might this look over a typical chemistry course?

 

At this early stage, for simplicity, I will look at when these fundamental concepts might be useful over the course of a typical chemistry course with traditional units. An outline is given below. I have starred what I believe to be the most important fundamental concepts for each unit. I may be wrong, and of course, all concepts are important pretty much all the time. But humans cannot think of everything at once, so it is important to prioritise! (Note: As I made this diagram, I also got thinking that bonding could be removed as a unit and be covered in the fundamental concept of electrostatic forces of attraction. It could be replaced by a unit titled something like “molecules, lattices and giant molecular structures”.)

 

When might these fundamental concepts reoccur throughout a typical chemstry course?

 

I would love to hear some thoughts on this. To what extent do you agree with this post and why? Are there any concepts that I have completely misunderstood? What might be something fundamental that I am missing? How might we organise and name units better? Any other thoughts?  

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