Tackling complexity – the importance of discussion

Helping a Year 12 chemistry student recently, we were going through some energetics questions as part of their preparation for summer mock exams.

The student loves their organic chemistry, but hasn’t found a similar connection with physical chemistry. During our discussions, it became apparent they hadn’t made strong connections between the three representations of chemistry – the macroscopic, submicroscopic and symbolic.

With organic chemistry, we have powerful modelling available with Molymods. These models, along with digital versions like molview.org, really help students to develop their understanding, engaging with concepts from multiple points of view. Physical chemistry doesn’t have something quite so visceral.

Some of techniques we used to develop the student’s understanding were:

• Dual coding – with a calorimetry questions, large quantities of written information needed processing. Converting this into labelled diagrams helps to process and summarise the information, and make a link to the practical they had carried out.
• Unit analysis – writing out in full the workings of calculations is high priority for mastering physical chemistry calculations. However, if a student is only learning to put numbers in the correct place and working mechanistically through procedure, they tend to come unstuck when questions are asked in different ways. We spent some time looking at the units of simple equations such as n=c.V, and discussing what is meant by mol.dm⁻³ in terms of physical quantities. We then looked at the more complex units of specific heat capacity, and used a bar model to make the link between the abstract unit and what 4.18 J.g⁻¹.K⁻¹ means at a macroscopic level.
• Articulating the meanings of symbols and technical phrases – when we, as chemistry teachers, write an equation like below, we see this very differently to ‘novice’ chemistry students. Our interpretation may be, for example, one mole of gaseous methane reacts with two moles of gaseous oxygen to produce one mole of gaseous carbon dioxide and two moles of gaseous water. The students may see methane and oxygen goes to carbon dioxide and water. The details contained in the equation is skated over. The use of the ‘+’ symbol with two different meanings in this one equation can cause confusion. Rather than just writing down the equation, we discussed each part in turn to elucidate their current understanding.

CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g)

• Looking at different ways to set out answers – with longer answer questions, a lot of students remain hesitant to use bullet points and flow diagrams. However, these are appropriate methods for working through scientific questions, make the student’s thinking clear, and are easier to check over for the students (and can be easier for teachers and examiners to assess).

This was an intensive revision session for the student, so we covered a lot of ground, and they made significant progress in their understanding. While not possible with a full class to the same extent, short, detailed discussion can form a key part of students development from novice to expert. Self-study by reading good-quality text books, and using systems like senecalearning.com are important in being exposed to and starting to assimilate the core ideas of the subject. However, I find it is the discussions between teachers and students (and between student peers) that make the critical progress from knowledge to understanding.