The meaning behind mechanisms

By Fraser Scott2017-08-09T11:53:00

Source: Pavelmidi / Shutterstock

What do students really understand from representations?

One thing that’s always bothered me about chemistry is the amount of information that’s hidden away in seemingly innocuous words or diagrams. For example, if I use the word ‘hydrogen’, do I mean a hydrogen atom or a molecule? Is it just one molecule or am I talking about a cylinder-full?

Mechanisms are even more complicated. There are lines for representing a pair of electrons and there are other lines for showing movement of a pair of electrons. Then sometimes we don’t even bother showing the electrons.

Imagine a student presented with a reaction scheme, something we use to represent a chemical reaction. If the student considers only the functional groups or reagents to understand how the reactants turn into the products, then they would be doing so using perceptual attributes only – a surface level interpretation of the information. But if the student considers the mechanism or formation of intermediates, they would be using relational attributes – a much deeper level of interpretation showing they can relate the representation to its meaning.

A recent study probed the perceptual and relational attributes that new chemistry undergraduate students use to categorise chemical reactions.

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