Sigma, Pi, Hybridization and Shape

Sigma bonds, Pi bonds. Shapes of molecules. Hybrid orbitals. How do they all fit together? I was really confused with this information when I was a student. It wasn’t covered when I did my biochemistry degree and I only felt like I really understood things until I started teaching about the concepts … so I really hope this blog post helps your understanding of things. Where do I start? Well, the three above concepts (Sigma & Pi, shape and hybrid orbitals) are, in my ...

The Year of the Periodic Table

In this post I cover some principles of TOK, NOS and the learner profile whilst focusing on our favourite chemistry friend, the periodic table. 2019 has been officially designated ‘The Year of the Periodic Table’. I often wonder who makes these decisions but this one was made at the highest level, by the UN – so I guess we can’t argue with that! Why 2019 though? Why not 2018, 2020 or another year? Well, the reasoning behind it is that this marks ...

What Is Entropy?

Entropy is covered in the AHL part of the course: Topic 15.1 in the energetics / thermochemistry unit. The entropy change (symbol = S) in a chemical reaction is determined by as follows: total entropy change = total entropy of products – total entropy of the reactants You will have probably been taught that entropy is a measure of disorder. Order goes to disorder. The universe is expanding (and therefore getting more disordered). Liquid water has a greater entropy than solid water (ice) ...

New Release: IB Chemistry SL & HL Option D: Medicinal Chemistry – Study & Revision Guide

We are happy to announce the publication of our new study and revision guide for IB Chemistry Option D: Medicinal Chemistry This book is a complete revision guide for SL and HL students preparing to answer IBDP Chemistry Paper 3 questions on Option D: Medicinal Chemistry. Focused on the syllabus requirements and with an emphasis on chemical structures to aid understanding, it provides the essential review, practice, and up-to-date advice needed to maximise marks in the exam.       Here’s what author Martin Bluemel ...

Teaching the Halogens: Some Ideas

How do you teach about the halogens? I am in the middle of teaching about them and thought it was worth telling you how I introduce the topic. I do like this topic as it provides lots of opportunities to link together parts of the course. Firstly, I will start with some theory, things such as the fact that the halogens are diatomic and are the only group whose members exist as solids, liquids and gases at room temperature. This then leads into ...

An Introduction to Equilibria

Equilibria can be a tricky concept to understand. In order to understand it, you need a good idea of reversible reactions and then a good idea of a dynamic equilibria. So, what is a reversible reaction? Put simply, it is a reaction in which products can be turned into reactants, but reactants can also be turned back into products. This can be shown using the ⇌ symbol: Reactants ⇌ Products For example, ammonium chloride will thermally decompose into ammonia and hydrogen chloride gases, but these gases will ...

Collision theory and mechanisms – linking it together

I’ve just started teaching the kinetics topic to my students and so far we have focussed on the collision theory. Have you heard of this? The collision theory explains to us what happens during chemical reactions in terms of the collision of particles. In order for a chemical reaction to occur, particles need to come together (collide) with sufficient energy (speed). This is called the activation energy (and is defined as the minimum amount of energy required for a chemical reaction). If ...

Making esters

We carried out a great lab in school today, making esters. Have you ever done this? What was good about it was that we used a good range of reagents and got some very different results. I set the class up with a range of alcohols and carboxylic acids and told them it was up to them what they wanted to make. We used microscale quantities for two important reasons: 1, As a safety precaution The beauty of using the microscale quantities is that ...

Teaching optical isomers

I've just started to teach this topic to my students. It doesn't take too long but I do find it an enjoyable topic to teach. But how do you teach it? I always warn the students that the topic is jargon heavy - the words / phrases used in the topic such as  chiral, racemic, racemate, optically active are all pretty specific to optical isomers and are not used outside of the topic. In my teaching I have found that students understand the ...

Optical isomerism

Optical isomers are hard to conceptualise. They are molecules with the same molecular formula and structural formula. They look exactly the same both on paper and in the real world. However, they only exist in pairs, it is only possible to get two optical isomers of the same molecule which makes things a bit easier to deal with (it should be notes that a molecule such as C5H12 has three isomers - not optical isomers but structural isomers, namely pentane, 2 methylbutane ...