This post is written by NKA.
I was lucky enough to attend the ResearchED meeting in Rugby at the weekend, and came back having learned a great deal. A session that had particular impact on me was lead by Ruth Powley: Planning curriculum sequences that enhance permanent learning in a linear curriculum.
Ruth referred to threshold concepts, which are the concepts that, once you “get” them, allow you to move to a higher level of understanding (they’ve been described as a portal, opening up a new and previously inaccessible way of thinking about something (Meyer and Land, 2003). I have been interested in the idea of threshold concepts since I read this article about their use in A level Chemistry teaching, and this one by David Didau, but I am still trying to work out exactly what they are, and how to use them most effectively.
Identifying threshold concepts in chemistry
As a first step, I have been trying to identify threshold concepts in Chemistry, so I can begin to plan lesson sequences based around them.
- Particles are “held together” in solids and liquids by forces. These have to be overcome for substances to melt or evaporate, and the strength of these forces determines the temperature at which this occurs. These “particles” might be individual atoms or ions, or they might be molecules. Therefore, when substances melt or evaporate, you might have to break “bonds” or you might have to overcome “forces”, and sometimes the bonds between atoms remain intact, even in a gas.
I’ve chosen this because it’s an idea that students find difficult to grasp at first, and I find I have to keep going back and reminding them of it as I move through the course. I’m not sure if my wording is great, I’m not sure if it’s actually a couple of threshold concepts combined, and I’m not even sure if it is actually a Threshold Concept! But it’s a start.
Another key idea within the same topic is:
- An electric current is a flow of electrical charge, and this charge can be carried by electrons (for example in a metal), but it can also be carried by ions. These ions cannot move when they’re held in a lattice, but they can move (and carry charge) when they’re in a liquid or in solution.
Again, I’m not sure whether this would be counted as a threshold concept or not, but I’ve decided not to get too hung up on worrying about this for now, and to just focus on ideas that I know students struggle with and move on at this stage.
Lesson sequences that enhance permanent learning
My next step is to plan these concepts into lesson sequences that will help pupils master them effectively. I also need to plan in opportunities for them to revisit the concepts, and practice applying them to different problems as we move through the course. Ruth reminded us in her talk that learning is liminal (it’s “messy”, see here). It doesn’t follow a straight “flight path” , and “there is no simple passage in learning from ‘easy’ to ‘difficult’; mastery of a threshold concept often involves messy journeys back, forth and across conceptual terrain” (Cousin, 2006).
So I am trying to design ways of revisiting the threshold concepts, of “chunking” learning, of spacing it out, and of interleaving topics (see, for example this page). Ruth suggested that, for each threshold (or core) concept, you plan stages within a lesson sequence where you can revisit it, and test it. For example:
- Practice 1
- Practice 2
- Practice 3
- Retrieval and testing
- Feed forward
These stages wouldn’t take place within a single lesson, hence where the sequence planning comes in. You would interleave these opportunities to practice into future lessons. I actually already do this type of thing, but I haven’t focussed specifically on threshold concepts before now.
Delivery- direct instruction?
I’m also planning how I will deliver these threshold concepts in the first place. Ruth argued that direct instruction, rather than “discovery” learning is optimal for “fast” (or efficient) learning (see Kirscher Sweller Clark), and suggested the following approach:
- Step 1: Worked examples. This avoids introducing a high cognitive load in the early stages. You should start with direct instruction, and give a series of examples, which are broken down into steps.
- Step 2: Self-explanation. Next, students should move on to self-explanation, so that they can rationalise the steps needed to understand a particular process.
- Step 3: Practice. Practice applying concepts to problems in a variety of contexts.
Ruth talked about germane load, which is the load placed on working memory by learning activities. Everything has a certain level of inherent difficulty, but how difficult you will find it as an individual depends on your previous knowledge. So if you build knowledge first, then you can use it more effectively later (see Renkl and Atkinson, also Evidence into practice for case studies).
Medium term plans
Ruth told us that she builds lesson sequences, rather than schemes of work, and that she writes medium term plans (MTP), rather than individual lesson plans. You need to “deliver information” at the start, and then practise it at spaced intervals, so that retrieval and practice of each concept can run throughout the MTP (see Carpenter 2012 for work on length of spacing).
An important point here is that content doesn’t always have to be delivered in person. You can, for example, flip certain aspects of the course content, so that you “buy” yourself time to use in lessons.Again, I already flip some of my lessons, so I will continue to plan this in as and when appropriate. I am also designing knowledge organisers, and I intend to use these in two main ways. Firstly, I want to set certain sections to be learned for homework (sometimes in advance of teaching about them) and secondly, I want to use them for regular low-stakes testing and retrieval practice (as described here).
Resources- comments and ideas?
This is where I’ve got to so far. I’d be interested to hear from anyone else who has thought about this, or wants to do something similar. I’ve started to collect resources together here. They’re very much a work in progress. I’d really appreciate comments and ideas.
I’ve added 2 columns to the lesson sequence I’m putting together for the department on Structure and Bonding. These columns are for threshold concepts and flipped learning/ knowledge organiser opportunities. I now need to plan in where I’ll revisit each threshold concept throughout the sequence, and how I’ll do this. I guess it could be as simple as finding suitable questions from the textbook for each concept.
I’ve started making a few ppts for when I “deliver” content, where I alternate between giving examples and setting questions/ problems, but I won’t do too much more of this until I’ve tried it out with pupils. I suspect this is an area I need to research and work on more.
I’m putting together a knowledge organiser to use with this module:
My dad happens to be teaching himself Chemistry at the moment (he was a linguist by profession, and didn’t study science to a high level at school). He has now reached A level standard, so it has been very useful to talk to him about ideas that he found difficult to grasp. For example:
- Oxidising and reducing agents
- Exothermic/ endothermic reactions, energy profiles, and equilibrium
- Hydrogen bonds (reason for lone pairs)
I will start to look at these next, I think.