A manifesto for the development of chemical common sense

‘Draw the structure of an alcohol which is resistant to oxidation.’

It’s a straightforward enough instruction, looking for the structure of any tertiary alcohol. A quick glance through the marking pile would show lots of students spotted this and correctly drew an OH group on a tertiary carbon. However, not all would get the mark. Some might draw the OH the wrong way, making the connection through the H, or, more likely, include a pentavalent carbon. These mistakes feel silly and they’re frustrating for teachers who might blame carelessness and a lack of checking.

Just because it’s not on the specification doesn’t mean it isn’t worth teaching

Sometimes silly mistakes are just that, silly. And even experts make them, as any teacher who has failed to balance an equation and had it pointed out by a 14-year-old will testify. But in novice learners so called silly mistakes always have a root cause: a lack of chemical common sense!

Chemical common sense is one factor that separates novices and experts. Over time – through practice, discussion and evaluation – experts develop automaticity in foundational areas of chemistry. It’s why we can often recall atomic masses, sometimes to several decimal places, and why we’re always eagle-eyed for a dodgy bond connection.

Just a silly mistake

In the early years of a student’s chemical education, development of chemical common sense can slip by unnoticed. Lots of examinations at age 16 will make allowances for slip-ups. For example, there may be two marks available for constructing an equation for the reaction of sodium and water, but students could still score one mark if their equation is balanced; the correct answer would be 2Na + 2H₂O → 2NaOH + H₂, but Na + H₂O → NaOH + H would still score students a mark. And this answer could arise from a lack of common sense with formulas or balancing.

Because a mark is awarded, the severity of this lack of common sense is overlooked. It doesn’t seem so bad as they didn’t lose all the marks. It’s dismissed as a silly error.

Consequently, the effect of a lack of chemical common sense is amplified for students studying chemistry post-16, even on into undergraduate studies. Certain concepts become assumed knowledge and don’t form part of the taught programme. This risks students losing many more marks – and not from the advanced content they’re learning, but from this basic common sense.

Fast-track chemical common sense

Developing chemical common sense begins in the 11–14 classroom, but is undermined by a system that focuses heavily on assessment. Resist the temptation to rush students towards the topics they encounter in their exams at age 16. Use the early years of chemistry education wisely. Give students breadth and expose them to as much chemistry as you can. These four approaches will help. 

Teach it

Just because it’s not on the specification, doesn’t mean it isn’t worth teaching. For example, one of the most popular 11–14 specifications in England does not outline a lesson on how to recognise apparatus and draw/interpret apparatus diagrams. Students don’t come from primary school knowing what a condenser looks like and art lessons don’t teach them how to do sectional diagrams of glassware. So in chemistry lessons we need to teach that, despite its conspicuous absence from syllabus materials.

You know your students and their contexts. Take the commercial schemes of work as your starting point and personalise them. Exam specifications are the minimum of skills and knowledge you should teach, not the maximum.

Scaffold development

Scaffold the development of chemical common sense. If you know your students don’t have automaticity in a particular area and you need them to have that knowledge at their fingertips for a lesson, provide it. Maybe as a well-chosen page in a textbook or a one-sheet knowledge organiser.

Bridge that gap

If you regularly find your 16–18-year-old cohorts lacking chemical common sense, develop a bridging unit before you begin advanced programmes of study. Check what basics they are fluent in and reteach where needed. This may seem a waste of time that could get in the way of progressing with the ‘real’ content, but it will save time in the long term.

Model thinking

And don’t forget to model your thinking. Because you have chemical common sense, it can be easy to skip modelling the correct thinking processes. When teachers model it, students pick it up for themselves.