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 ...

Synthesis of Aspirin

Aspirin has been with us for long time - the first documented reports of its use occurred over 2000 years ago. That said, the aspirin may not be in the form that you instantly think of (ie, a tablet) but it has been used all the same. Aspirin is an analgesic, which means it has pain killing effects and it has been well documented that the ancient Egyptians used a special tea made out of willow bark to treat a number ...

Practical application of the ideal gas equation

How many moles of air are in your lab? What mass is this air? These are a couple of great questions you can set your students and ask them to come up with some answers using the ideal gas equation. You will need a barometer (to determine the air pressure), a thermometer (to determine the temperature of the lab) and a rule to calculate the volume of the lab and hopefully some imaginative students. I carried out this work with my class a while ...

PRE IB: Practical work – good practice

This blog was written by Dave Allen, an experienced IB Chemistry teacher. To read more Chemistry blogs for students and teachers, click here. This is the fourth and final blog post on pre-IB Chemistry. I do hope you have found the mini-series interesting and helpful, hopefully it will have talked you into deciding to follow chemistry at diploma level! This blog post will involve an introduction to lab (practical) work at IB level. You may or may not be aware that your IB ...

PRE IB: The Basics – Bonds

This blog was written by Dave Allen, an experienced IB Chemistry teacher. To read more Chemistry blogs for students and teachers, click here. Knowing your bonds (and structures). This blog post will (hopefully) refresh your memory on bonds and structures that you will need to familiar with in IB Chemistry. Firstly, the bonds When atoms join, we say they ‘bond’ and electrons are the part of the atom that are involved in bonding. There are two types of bond that this blog post will cover: Ionic ...

PRE IB: The Basics – Moles

This blog was written by Dave Allen, an experienced IB Chemistry teacher. To read more Chemistry blogs for students and teachers, click here. Yes, you have read that correctly – we get moles in Chemistry as well as Biology. However, our mole is not the small furry type – it's a number! You see, in Chemistry we count things not the obvious way (i.e., 1, 2, 3, 4, 5 and so on) but by using a word – the ‘mole’ – to represent ...