In Praise of Alex Johnstone; He made me realise I was not alone


Our research shows that pupils at all stages were complaining about the same areas of the syllabus – energetics, the mole, balancing equations ionic equations and parts of the organic chemistry…….The factor common to all these areas was that they were being taught in a fashion which overwhelmed the short-term memory.

On realising that I am a teacher of chemistry, I am regaled by people with of tales  experiments going wrong when they were being taught. (It might be the best part to them but not to me in my role as a safety consultant with CLEAPSS.) They often add that they never understood what was going on especially with equations. I suspect that most chemistry teachers are subjected to this.

That statement at the beginning is from the Introduction of Chemistry About Us by Alex Johnsto ne, Norman Reid and Ian Morrison. It was written about 1979 (it could even be written now) and Alex was then in education research, Ian was a Local Authority Science Adviser and Norman was a teacher. In 1964, Alex, then the teacher, and Ian, the Teacher trainer, had developed Chemistry Takes Shape (Vol 1-5). They, like the some teachers in England in the Nuffield Foundation, could see that the content of the chemistry curriculum and the methods used to teach it in secondary schools had barely changed since the 19th century. Rote learning tended to mean that students understood little of what they had learnt. Students needed to experience science for themselves through practical work, rather than just reading about it.

I was at a meeting of 40 chemistry teachers about 5 years ago, having been invited to do a microscale workshop. I went into a talk by Dr (now Professor) David Read of Southampton University. David asked the teachers “How many of you have heard of Johnstone’s triangle”.


David is modern; he has electronic measuring equipment and they had to make a decision and press a button, so we saw the answer immediately. Only one teacher had heard of it. When he put the triangle on the board, you could see flashing light bulbs coming from 39 heads. In this simple diagram, Alex Johnstone encapsulated the issues of teaching chemistry. The part of chemistry that everyone loves consists of the explosions, the fire, the sparks, the sudden red-hot glows, liquefied gases and the colour changes. Chemists rank as the great entertainers of the sciences from Humphrey Davey to Dr Hal. The Royal Institution Christmas lectures seem determined to show a hydrogen balloon bursting with fire even if the subject is about language as in the 2017 Christmas lectures (see below). Getting the students to think about the interaction of particles and applying measurements and maths is far more difficult.

RI hydrogen bang

The initial impact of this triangle to the teacher is one of comfort and reassurance. To me it means “I am not alone; other teachers have the same issues as I have but we have all been afraid of uttering them as it could imply I am a bad teacher to outsiders (inspectors, observers, parents students and even the press)”.

Alex suggests that teachers tackle two sides at a time to students when introducing a new topic. It requires a huge amount of consolidated knowledge and practice to deal with all three aspects in one lesson. This is why chemistry should be revisited at regular intervals to cement and consolidate the knowledge in the long-term memory.

Of course, some like to extend the triangle to a tetrahedron. Peter Mahaffy calls the fourth point the “human element”[i].

Simple johnstone traingle
The Johsntone triangle on the left with the Mahaffy extension on the right to make it a tetrahedron

I do not think Alex would not approve of the word “elements” in this context as it would cause conflicting “noise”, with the word being used in a different context in chemistry, but he would approve of the extension. He wrote at the beginning of the last Chapter of “Energy, Chaos, and Chemical Change[ii]” which is entitled “Thermodynamics and Every Things”, published in 1977, “The work in this book will remain largely an academic exercise unless we can see it operating in the world at large.”

Here is another quote[iii] about the order in which we teach chemistry.

Begin where the students are. From an information processing point of view, begin with things that they will perceive as interesting and familiar so that there are already anchorages in their long term memory on which to attach the new knowledge. Do we begin in the traditional way with salt, sodium carbonate, silver nitrate and barium chloride OR do we begin with petrol, camping gas, plastics and foods? Organic chemistry has traditionally been thought of as too difficult for beginners, but a moment¹s thought will show that it is not necessarily so. We are beginning with the macro and can afford to take in some submicro.

In Chemistry Takes Shape, the first experiment is not about the Bunsen burner but evidence for particulate theory using purple potassium manganate(VII). This is carried on throughout the series with the model being gradually adjusted, improved and more complex, as new “macro” evidence becomes available. After introducng particles the books moves to the chemistry of oxygen, hydrogen and water but particles are always there. I notice that in a current KS3 syllabus, the particulate model is present in the first module but subsequent sections make no mention of it at all. Students will not be seeing the full picture and it will not be present in their long-term memory when it comes to further development in KS4 and post 16.

Keith Taber’s[iv] paper shows how the triangle is adjusted and improved in light of recent research. He divides the macro section (blue) into 2 because the macro concept of elements and compounds, purity etc are just as remote from students as the observed macro event. The symbolic section (green) is divided into 3. A chemical formula (C2H4) can be used to represent a substance and molecular formula. The only way I can really understand this is to redraw it myself (with extra topics) and I hope I do it justice and there will be constant debate as to whether a topic is in the right box.Taber extention of triangle

It is right to extend the idea of the triangle under the realms of research  but that will inevitably bring more complexity as seen above. That happens in chemistry itself. I can teach the chemistry of ethene quite adequately without going into complex molecular orbital theory. Similarly the original triangle might now be more limited, but it is an iconic representation of the problems facing the chemistry teacher.

So let us remember with whom it started; Alex Johnstone, 1930 -2017[v].


[ii] Energy, Chaos and Chemical Change, Heinemann Educational Publishers (1977), ISBN-13: 978-0435655259


[iv] Revisiting the chemistry triplet: drawing upon the nature of chemical knowledge and the psychology of learning to inform chemistry education, Chem. Educ. Res. Pract.,2013, 14, 156



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