I have written about this work in a series of blog posts and on a poster for MICER, but this post summarises the first part of my talk from ResearchED in Rugby this weekend. For speed, I haven’t referenced every single point here, but my reading list can be found here.


I’m a Chemistry teacher and Research Lead, so this talk was very much put together with both hats on. I want to relate a little bit about why I find the idea of Threshold Concepts so interesting, but also to outline my attitude to Research-informed practice in general.

Earlier this year, I was teaching a year 10 review lesson about Structure and Bonding. I was pretty confident that the group had grasped the main ideas. They could tell me about the properties of ionic compounds, about why they can’t conduct electricity when solid (the ions are not free to move, because they’re held within a 3D lattice structure), but they can conduct electricity when molten or in solution. In general, they used the correct scientific language in classwork, homework and AfL checks. I thought it was all going quite well.

But then one of my pupils asked me how it was that a lattice could form, when there were only ever 2 ions reacting. I was a bit flabbergasted, and couldn’t understand why she could think that…. until I realised that when we teach ionic bonding, we start of with dot/ cross diagrams. And these diagrams model the formation of ions using only one or two representative atoms/ ions (as above).

This particular pupil understood the concept of ionic lattices and their properties. She could also draw dot and cross diagrams to show how ions form. But she hadn’t (yet) put these ideas together. I hadn’t made that link explicit enough for her to connect the ideas herself.

I re-explained that every reaction involves millions (billions!) of atoms and ions, and that the dot/cross diagram represented the process in just two of these. I saw a “lightbulb” come on in her head. It was a very rewarding moment.


If you ask teachers why they chose such a demanding (and sometimes thankless) career, they will often tell you that they wanted to switch lightbulbs on in people’s heads. It’s such a beautiful thing when you see a pupil suddenly “get it”. Especially if they have struggled with “it” at first.

This is why the idea of Threshold Concepts was such an attractive one for me when I read about them last year in Education in Chemistry magazine. Threshold Concepts have been described as a portal to new and greater understanding. Once you’ve passed through them, there is no going back, and you can access and understand concepts that were previously inaccessible.


We know as Science teachers that conceptual understanding and sequencing is important. For instance, to explain why ionic compounds can conduct electricity when molten or in solution, pupils first have to understand that the ions in the liquid will move when a potential difference is applied. But they also have to appreciate that the current that then flows is different to the one they think about in year 7 Physics (for example), when they talk about the movement of electrons in a metal wire.

These are all tricky and important concepts for pupils to understand. But Meyer and Land distiguish between difficult/ core concepts and Threshold Concepts. And pupils wouldn’t be able to understand any of the key conepts above if they didn’t realise that the ions present in the giant ionic lattice remain as charge particles even when the lattice structure is broken down and the compound is melted or dissolved. I see this as a potential bottleneck, maybe even a Threshold Concept.


In their 2003 paper, Meyer and Land describe the characteristics of Threshold Concepts. They are transformative, probably irreversible, help you make links between apparently unrelated things, and they are troublesome.

Most importantly, from the point of view of a teacher, they are often tacit among experts, and we therefore might not think to teach them explicitly. Glynis Cousin also talks about the difficulty of putting yourself in a novice’s shoes, and remembering the ideas that you once struggled with.


So I put out a tweet to see if anyone would be interested in looking at these with me for Structure and Bonding (because this was the topic I’d been tasked to write a Scheme of Work for). I thought that if I could any Threshold Concepts, I could anticipate them and plan for how I’d teach them.

Nobody could really point me to anything relevant to my chosen topic, and I began to wonder if anything actually existed out there in the literature. However, a couple of people suggested using Misconceptions literature to identify the main sticking points in the topic, and to go from there.


Luckily, there was a wealth of really helpful sources available freely online, many via the Royal Society of Chemistry.


I started to gather the common misconceptions together into a spreadsheet, and from here I formed a list of common tricky concepts. My idea was to identify, anticipate and plan for these sticking points, and to get an idea of which misconceptions were most pervasive, to try and determine which of them could be classified as possible Threshold Concepts.

In the next part, I shall talk about my attitude and apporach to research-informed practice, as well as the ideas from Cognitive Science that I applied to my teaching. In part 3, I shall explain what happened when I taught and reviewed the topic, with 4 classes from 3 year groups. I’ll also suggest some approaches that might help students access the more difficult ideas within Structure and Bonding.