Energy Language Thoughts Part 1

14Feb17

I was thinking ‘out loud’ on Twitter about the ‘new’ energy language, discussions prompted in part by science teachers applying the changes in their classrooms. I know I’ve blogged about energy before, but thought it might be time to have another crack at it. I’m not writing here in an official IOP capacity, although I’m also swapping these ideas with colleagues. All thoughts, responses, criticisms and offers of coffee accepted. And if you add the comments here it will be easier for others to join in, as twitter replies get lost after a while. Alternatively, as the responses to a twitter poll led me to post it in chunks, you might want to wait until it’s all done. I’ll crosspost the complete thing to TalkPhysics as well.

Challenges

  • Resistance to change – teachers as much as students!
  • Students who have learned one approach in KS3 and are now being told something different for KS4.
  • The exam boards can’t seem to agree on which stores to use and which to omit, which has knock-on effects for textbooks.
  • Teachers don’t know which answers will get marks in the exams, so don’t know what advice to give students.
  • Existing resources are incompatible with the new language – but with enough similarities to make it look like they’ll work (like a false friend in language teaching, which gives you confidence while misleading).

I don’t have answers for these. To be honest, nobody does! What I can say is that many people are trying to figure out the best way to make these changes work well for everyone. It is, in my personal view, unfortunate that they are coming in with both a specification and a grading system that are new. It’s worth noting the stores and pathways model hasn’t been recently  invented by the IOP to annoy teachers. For example: Robin Millar, Practical Physics.

There’s lots on the Supporting Physics Teaching resource from the IOP, but one place to start is this suggestion about useful things to keep in mind.

Hopefully Helpful Thoughts

A good thing about the ‘new’ language is that it encourages – pretty much demands – more attention on the actual physics. That’s the point. What is happening? So let’s start there; in any example, what process is involved? Some materials/sources call these pathways, but the idea is the same. Let’s not get hung up on labels for them, but on descriptions of actual events. It may help to emphasize to yourself that they are verbs, not nouns. They can happen fast or slow. But they involve actual physics, forces and EM and heating and so on (obligatory link to the Big Ideas of Science Education, because it’s awesome. When I rule the world every school science lab will have a huge poster of these.)

Now, these processes will change something. It means we can measure something which is different after this process compared to before. We’re not interested, right now, in how quickly this change has occurred – just that it has. This is a change – maybe a temperature increase, a greater separation of two objects, whatever – in a measurable quantity. This is associated with what we call a store. Different kinds of store have different equations, which link the measurable quantities together along with some constants. The result of that equation is a value for the energy associated with that store.

If we pay closer attention, we find that (at least) two stores have changed. What’s really interesting is that if we’re really careful, when we compare the equations, we find that the numbers are the same. An increase in one store is always balanced by a decrease in the other. The equations work as an exchange rate, showing how temperature rise in one part of the system is ‘worth’ faster movement in another part.

This, of course, is the principle of conservation of energy. Energy isn’t lost. But we can lose track of it. Sooner or later, the processes end up heating up the entire universe. Because the universe is pretty big (no, bigger than that) the change in temperature is effectively immeasurable.

So there we are; a very brief introduction to the ‘new’ model. More posts coming up, hopefully one per day. The sooner you comment, the more likely I can address your suggestions in the course of the series!

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10 Responses to “Energy Language Thoughts Part 1”

  1. 1 Helen Rogerson

    I am struggling to get on board with the stores/pathways model of energy. I have read a lot of information about it and see what you have written here as a good overview of what I understand to be the purpose.

    I think that at key stage 3 I want more simple examples. Everything I come up with seems to start with a chemical store and end up as the thermal store in the surroundings! Some of the changes, especially those involving pathways instead of stores I struggle with. For example a motor lifting a mass, or a torch. Where do light and electricity fit?

    • Helen, thanks for commenting – especially so late at night! This first part was indeed intended as an overview, and later pieces are looking at aspects in more detail. One of those is about practical examples, both hands-on and demonstrations, that might be helpful in classrooms!

      The old model was all about one change, from one ‘type’ of energy to another. That meant there was only one approach possible. With time to think and play around, I’ve come to understand that you use the ‘new’ model in two very different ways, and I’m not sure that’s necessarily clear.

      1: Take a ‘mental snapshot’ before and after an event or process. Students record values of relevant quantities, eg temperature, before and after. We can then describe what is happening in terms of stores that have been filled or depleted, and perhaps calculate changes in Joules by using the equation(s).

      2: Consider the process first; what is happening? This is about the physics, and can still be quantitative – it’s power, so duration and rate are clearly vital – but doesn’t necessarily tell us what the end result will be.

      In the end, of course, our students need to be happy with both aspects to get a proper understanding. The question is which starting point is more helpful.

      To preview the discussion about good choices of examples; the important thing is to choose the right snapshots, rather than a specific toy or event. We’ve all had kids faced with a torch in an energy circus and not knowing which ‘type’ to start with! A ball at the top of a ramp starts with a filled gravitational store. A wound up toy has a filled elastic store. A hot cup of coffee – mmm, coffee… – has a filled thermal store. You’re absolutely right that eventually, all processes end up with the thermal store. So we need to take our ‘after’ snapshot earlier, when the ball is rolling down the hill (kinetic store), the toy has climbed the slope and stopped (gravitational store), the coffee has cooled down (thermal store, but of the surroundings not the coffee).

    • Light, sound and electricity (defining electricity as a movement of charge) can’t be stored and that is a really important point. That’s why they are transfers. To store electricity you have to change it into chemical energy i.e. a battery.

  2. 4 Amy Morey (@PurpleSciChaos)

    I was lucky enough to have some IoP training in my last school, which meant that I ‘thought’ I had my head around it, but didn’t get a chance to teach it the ‘new way’. Having moved schools, when it came to teaching this topic, I asked the Head of KS3 how he wanted me to teach it. His reponse was – “Well the end of topic test has questions on the old way, so they’ll need to know that!” In the end, I’ve tried to teach a mix of both, hopefully successfully? (Out of interest, after our discussion, I passed the information on to him, and his response was – don’t tell the others – I don’t want to scare them!)
    When teaching it, I’ve ended up using battery icons similar to the ones that all kids are familiar with on their mobile phones. We can identify the store and then at various points on the pathway take a ‘mental snapshot’ as you call it, and draw in what the ‘battery level’ is for that store at that moment. I had a very low ability set, so just used qualitative amounts, however for a higher ability set I would consider including squares or bars within the batteries so that they could quantify them. I was surprised at how ‘easily’ they understood this concept. Even introducing it with the standard ‘how much energy is in food?’ practical they were able to use the stores and the battery levels to say what was happening! Perhaps I should put my worksheets/batteries on TES or my blog etc for people to use or at least think about how to show it? but I think that’s something for the future?

    • Amy, thanks for taking the time to comment. I know that many schools don’t seem – despite the specification change, and the materials from IOP, articles via ASE and so on – to have taken the language changes on board. I think part of it is that the wording is just similar enough that they think they already do it. The understandable concern right now, for many teachers (and us!) is how the exam boards will deal with a variety of approaches in 2018. I hope this piece, and those that will follow over the next few days, might be usefull for you to share with colleagues.

      I like the idea of using something familiar to the students – and would certainly be interested in hearing more about these battery icons in use! They can of course be charged up in more than one way (mains, PV cell, hand-winding) and discharge through several possible routes. The only danger – and this is something that is a general point – is that in most cases a physics energy store can’t be full, as such – only filled or depleted. What we’re getting towards, of course, is the relative change in energy each time, delta-E. Thanks for sharing that and please do send me the link if/when you blog it in more detail!

  3. The thing I have the most problem with is the definitions of the stores and how different exam boards, textbooks and revision guides use a different set of names for them.

    • Jenny

      Thanks for your comments – and I know exactly what you mean! The variations in the chosen stores is dealt with in what is currently Part 3, coming by the end of the week. I agree that the inconsistency is frustrating, and when I rule the world things will be different. But in the meantime, I can only point you towards the always-relevant xkcd on Standards.

  4. 8 Richard Needham

    It would help to fix the language issues here to avoid further confusion – pathway or process?
    The biological implications of adopting this model are significant. Biologists talk about energy flow, using light energy for photosynthesis, and the energy content of food. All three of these (and others) need to be clearly described (and adopted) using a store/pathway model if pupils are to successfully achieve your goals.

  5. Richard, thanks for the comment – and apologies that I didn;t reply when I’d said I would.

    1 I completely agree that having two terms meaning the same thing is unhelpful. For myself, I prefer ‘process’ – and several sources seem to use it too. The IOP materials mostly use ‘pathway’. The difficulty is that IOP is getting the blame for inconsistency in how people are using their materials, for example the different exam boards and their varied lists of stores!

    2 Biology issues are not insignificant, but I don’t think they’re insurmountable. I agree we need better shared language if we’re going to get anywhere. I’m rearranging the order of your examples:

    Energy content of food is straightforward: it’s an example of a chemical store, just like always. Different foods provide different amounts of energy per gram, which is fine. The ‘use’ of the energy is about the combination of pathways; as I wrote in Part 2, describing metabolism and the shifting of energy between chemical stores eg glycogen and glucose fits the model. Emphasizing that the four pathways are the most common *physics* examples, but adding a ‘reacting’ pathway category which would include combustion, metabolism, digestion etc helps. I’m going to look for more information on this.

    I’m presuming by energy flow you mean in food chains. Arguably ‘A eats B’ is another example of a biology-specific pathway that would fit under the ‘reacting’ category. The energy shifted is either a discrete amount (ie from the rabbit’s biomass to the fox) or would be a daily or weekly rate. Either way it fits the model. Other pathways account for shifts from the prey biomass chemical store to the environment.

    The light energy for photosynthesis is, in some ways, the easiest to resolve. The light is the pathway delivering the energy to the chemical store – glucose, in my physicist’s understanding of a very simple model of photosynthesis. The ‘source’ store is, in some ways, irrelevant to the biology, as long as the pathway is sufficiently intense (ie rate or power) and of the right wavelengths (which kind of radiating’ pathway it is).

    I think. More consideration to come – please, more responses and corrections welcomed!

    • 10 Richard Needham

      I wrote something around these issues in School Science Review (Sept 2014 vol 96 number 354 pp74-77). Unfortunately my thinking has not got much clearer since then!
      Energy content of food – no – energy is within the substrate /oxygen system and we should consider the breaking and making of chemical bonds – but not at KS3. If we do not want youngsters to think of energy to think of some form of substance that can be released when a fuel is ‘broken down’ then we may need to be more careful as describing fuels as containing energy.
      This thinking about energy as some sort of ‘stuff’ links to energy flow in ecosystems – the term creates ideas around energy being a substance a bit like water trickling down a slope – some reaches the end but most has drained away. The language gets in the way of understanding principles such as the conservation of energy.
      As for photosynthesis (at post 16) I really struggle to explain changes in photosystems I and II, the release of hydrogen ions for ATP synthesis etc using stores and processes ideas.
      I am impressed by your bravery! Well done.


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