Equation recall test

This was supposed to be a really quick job. For something I’m working on, I was looking at the equations students need to recall for the GCSE Physics exam (specifically AQA). And it annoyed me that they weren’t in a useful order, or a useful format for testing. So I’ve made a testing sheet, with pages for Energy, ‘mostly Electricity’ and Forces.

There are four columns, which are blank in the first three pages (for students) but completed in the answer sheet version. Because I’m good to you.

Download eqn testing sheets as PDF

Equation for…

I’ve given the word, not the symbol – thoughts? (Could/should that be another column?) I’ve removed a couple of what I see as duplications, and missed out momentum because I was thinking of this as for everybody. Plus it would have mean adding another row and I was sick of messing with formatting.

Which variables are involved?

For students to write in the variables in words, as a starting point. The idea would be that you can give partial credit for them getting part way there, because we should recognise the early stages of recall. You may off course have them skip this bit later on.

What are the symbols?

If they know the variables, can they write down what they will look like in the equation? This would be the other place for them to show they know what the ‘equation for…’ variable could feature in symbol form.

Equation

Formatted as best I can, in a hurry in Publisher. I’ve used the letters as listed on the formula sheet, p95 of the specification. Even when I disagree.

As ever, please let me know if/when you spot mistakes. Because it’s in Publisher I can’t upload the editable version here, but drop me a line in the comments if useful and I’ll send it your way.

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Measurable Outcomes

Following a conversation on twitter about the phonics screening test administered in primary school, I have a few thoughts about how it’s relevant to secondary science. First, a little context – especially for colleagues who have only the vaguest idea of what I’m talking about. I should point out that all I know about synthetic phonics comes from glancing at materials online and helping my own kids with reading.

Synthetic Phonics and the Screening Check

This is an approach to teaching reading which relies on breaking words down into parts. These parts and how they are pronounced follow rules; admittedly in English it’s probably less regular than many other languages! But the rules are useful enough to be a good stepping stone. So far, so good – that’s true of so many models I’m familiar with from the secondary science classroom.

The phonics screen is intended, on the face of it, to check if individual students are able to correctly follow these rules with a sequence of words. To ensure they are relying on the process, not their recall of familiar words, nonsense words are included. There are arguments that some students may try to ‘correct’ those to approximate something they recognise – the same way as I automatically read ‘int eh’ as ‘in the’ because I know it’s one of my characteristic typing mistakes. I’m staying away from those discussions – out of my area of competence! I’m more interested in the results.

Unusual Results

We’d expect most attributes to follow a predictable pattern over a population. Think about height in humans, or hair colour. There are many possibilities but some are more common than others. If the distribution isn’t smooth – and I’m sure there are many more scientific ways to describe it, but I’m using student language because of familiarity – then any thresholds are interesting by definition. They tell us, something interesting is happening here.

The most exciting phrase to hear in science, the one that heralds new discoveries, is not “Eureka!” but “That’s funny …”

Possibly Isaac Asimov. Or possibly not.

It turns out that with the phonics screen, there is indeed a threshold. And that threshold just so happens to be at the nominal ‘pass mark’. Funny coincidence, huh?

The esteemed Dorothy Bishop, better known to me and many others as @deevybee, has written about this several times. A very useful post from 2012 sums up the issue. I recommend you read that properly – and the follow-up in 2013, which showed the issue continued to be of concern – but I’ve summarised my own opinion below.

phonics plot 2013
D Bishop, used with permission.

Some kids were being given a score of 32 – just passing – than should have been. We can speculate on the reasons for this, but a few leading candidates are fairly obvious:

  • teachers don’t want pupils who they ‘know’ are generally good with phonics to fail by one mark on a bad day.
  • teachers ‘pre-test’ students and give extra support to those pupils who are just below the threshold – like C/D revision clubs at GCSE.
  • teachers know that the class results may have an impact on them or the school.

This last one is the issue I want to focus on. If the class or school results are used in any kind of judgment or comparison, inside or outside the school, then it is only sensible to recognise that human nature should be considered. And the pass rate is important. It might be factor when it comes time for internal roles. It might be relevant to performance management discussions and/or pay progression. (All 1% of it.)

“The teaching of phonics (letters and the sounds they make) has improved since the last inspection and, as a result, pupils’ achievement in the end of Year 1 phonics screening check has gradually risen.”

From an Ofsted report

Would the inspector in that case have been confident that the teaching of phonics had improved if the scores had not risen?

Assessment vs Accountability

The conclusion here is obvious, I think. Most of the assessment we do in school is intended to be used in two ways; formatively or summatively. We want to know what kids know so we can provide the right support for them to take the next step. And we want to know where that kid is, compared to some external standard or their peers.

Both of those have their place, of course. Effectively, we can think of these as tools for diagnosis. In some cases, literally that; I had a student whose written work varied greatly depending on where they sat. His writing was good, but words were spelt phonetically (or fonetically) if he was sat anywhere than the first two rows. It turned out he needed glasses for short-sightedness. The phonics screen is or was intended to flag up those students who might need extra support; further testing would then, I assume, suggest the reason for their difficulty and suggested routes for improvement.

If the scores are also being used as an accountability measure, then there is a pressure on teachers to minimise failure among their students. (This is not just seen in teaching; an example I’m familiar with is ambulance response times which I first read about in Dilnot and Blastland’s The Tiger That Isn’t, but issues have continued eg this from the Independent) Ideally, this would mean ensuring a high level of teaching and so high scores. But if a child has an unrecognised problem, it might not matter how well we teach them; they’re still going to struggle. It is only by the results telling us that – and in some cases, telling the parents reluctant to believe it – that we can help them find individual tactics which help.

And so teachers, reacting in a human way, sabotage the diagnosis of their students so as not to risk problems with accountability. Every time a HoD puts on revision classes, every time students were put in for resits because they were below a boundary, every time an ISA graph was handed back to a student with a post-it suggesting a ‘change’, every time their PSA mysteriously changed from an okay 4 to a full-marks 6, we did this. We may also have wanted the best for ‘our’ kids, even if they didn’t believe it! But think back to when league tables changed so BTecs weren’t accepted any more. Did the kids keep doing them or did it all change overnight?

And was that change for the kids?

Any testing which is high-stakes invites participants to try to influence results. It’s worth remembering that GCSE results are not just high-stakes for the students; they make a big difference to us as teachers, too! We are not neutral in this. We sometimes need to remember that.


With thanks to @oldandrewuk, @deevybee and @tom_hartley for the twitter discussion which informed and inspired this post. All arguments are mine, not theirs.

CSciTeach Evidence

It’s odd, in some ways; for a profession which is all about leading and tracking progress for our students, we’re remarkably bad at agreeing any kind of consistent way to record what we do.

Years back I put together a Google Form for me to record what I was doing. The idea then was to match different activities to the Teacher Standards. To be honest, I didn’t use it for very long, although the process was useful in itself. Since then I’ve thought several times that a better way to track what I do is in the context of professional accreditation. For science teachers, who I work with in my day job, there are several things to consider for CPD tracking.

  1. Performance management forms are very specific to institutions, but in most cases having a record of what’s been done in between school-based INSET would help.
  2. There are several ways for a science specialist to become accredited; this is about recognising current knowledge and skills, not jumping through new hoops. CSciTeach is the route I chose, through the ASE (now also available via RSC and RSB). You may also wish to consider the new STEM Educator pathway. I have just completed the Chartered Physicist accreditation, which is available to physics teachers and teacher-trainers with appropriate experience. (I should point out I’m involved with making this better known to teachers/teacher-trainers and more information, exemplars etc will be out this autumn.)
  3. Having this information to hand can only be a good thing when it comes time to apply for new roles. I personally think it’s bizarre that there isn’t a single national application form, universal* with perhaps a single page ‘local detail’ for stuff a school feels just has to be asked. Otherwise colleagues have to waste time with many tiny variations of badly formatted Word forms, rather than their cover letters.

The thing is, who writes down every time they read/watch/observe something which ends up in a lesson? And if you do make a note of it, mental or otherwise, what are the chances of it being recorded in one central place? We end up with a formal record which has a few courses on it, and all the other ideas are along the lines of:

I think I got it at a teachmeet – was it last year? Might have been the one before. I’m pretty sure there was an article, I’ll have a look for it in a minute…

 


 

My Proposed Solution

What I’ve produced didn’t take long, and it’s only the first version – I’d really welcome ideas and suggestions for how to improve it. The idea is to gather information, reflect on impact and be able to refer back to it as evidence of professional practice.

If you want to try out the form, then feel free – this link takes you to my trial version and is not linked to the downloadable version below. You can also look at (but not edit) the resulting spreadsheet; note that the ASE guidance is reproduced on the ‘Notes’ tab. Thanks to Richard Needham aka @viciascience for some suggestions.

I’ve used the CSciTeach standards, but obviously (1) you need to do more than this form to be accredited and (2) other accreditation schemes are available.

Slide1

Slide2


Want to play around with your own version, editable and everything? You’re in luck:

1 Set-up

You’ll need a Google account. Go to the responses sheet (starting here means the formatting of the final spreadsheet is preserved.) Select ‘File’, then ‘Make a Copy’. Choose ‘Form’, then ‘Go to live form’; save the form URL as a bookmark on each of your devices. The spreadsheet URL will probably be most useful on something with a keyboard, but YMMV.

2 Capture

The form is set-up to get a few brief details fast, and then gives the option to skip to ticking relevant CSciTeach standards. If preferred, you can add the details of your reflection and impact in your setting at the same time. This completes the entry, but often you’ll want to come back when you’ve had a chance to think or try something out with students.

3 Reflect

Assuming you skip the in-depth reflection during step 2, you’ll want to return to the spreadsheet the form generates. I’ve included a few formatting points to make it work better which should be preserved when you copy it.

  • Column headings are bold
  • Columns are sized so it should print neatly on landscape A4
  • Text is justified ‘left, top’ and wrapped to make the columns readable
  • If empty, the columns for further reflection and impact are shaded red to prompt you to fill them in
  • The standards cells are shaded if at least one in that category has been ticked.

The point of CSciTeach, or any other accreditation is to recognise that ‘doing CPD’ is not a one-off event or course. Instead, it is a process, and one which should have reflection and consideration of measurable impact at its heart. This impact may be on students, teachers or both. This will very much depend on your role.

4 Share

You may prefer to keep the spreadsheet for your own reference only, using it to fill in other forms or complete applications. Sharing a Google spreadsheet is easy enough, of course; that’s the point! Just be aware that if you give ‘edit’ access, whoever it’s shared with can change your details. If you want their input – for example a professional mentor or coach – it might be better to give them permission to ‘view and comment’.

Alternatively, you might wish to search for particular examples and copy the results to a fresh document, depending on context. It would be easy to modify the form so that the Stimulus question was multiple choice, allowing you to categorise different kinds of formal and informal CPD. If colleagues think this would be more useful, I’ll create an alternate version centrally.

If, as a HoD or similar, you want to try something like this collectively, then it would be easy to adapt. Give the form URL to all team members and ask them to contribute. Whether you wish to add a question where they identify themselves is, of course, a more sensitive issue!


 

What Next?

Firstly; tell me what might be worth changing using the comments below. If I agree, then there’s a fair chance a version 1.1 will be shared soon. If you’d rather play around with it, feel free. I’d appreciate a link back if you share it.

Secondly, there are a couple of features which would be great to add. Being able to upload a photo or screenshot would be much better than copying and pasting a link, but I can’t see how to do this with a GForm. Related, if you think this could be developed into a mobile app then I’m sure the ASE would love to hear from you.

Lastly, yes, the SNAFU above* was on purpose. Those readers who understood can feel smug for exactly five seconds.

#ASEslowchat Tuesday: Practicals


I can’t comment on what is happening in my classroom, or my department. Because I don’t have a classroom; instead I work with teachers in their classrooms, supporting their departments. So most of what I’ll be sharing will be at one step removed, but it is based on what ‘real’ teachers have told me is happening in their schools. I’ve played around with the stimulus questions a little.
Which required practicals have you completed with your classes; have you only completed these, or gone beyond them? Why?

I posted a little while back about how I felt the required practicals should fit into a balanced science curriculum. (This was a different post to one from even earlier, based o a draft of the AQA required pracs.) Nothing I’ve seen has caused me to change my mind. The summary is that whether a practical is required or not it should be used in the same way; to support teaching of science content and skills. It might, of course, be worth returning to the required practicals as part of the organised review/revision schedule, because they’re effectively content. Until then, ask the same questions, practise the same skills, as you would for any practical. (And, of course, don’t neglect these aspects if a practical is ‘unrequired’!)

Has the GCSE impacted on the work of the technicians in the department? Have you had any issues with equipment?

Not being in a school full-time, I’m not sure about the workload side of this. I don’t think it’s been a huge issue – certainly compared to lots of ISAs to worry about! (I hope school technicians are being encouraged to contribute to this topic, by the way.) But I have been doing a fair bit about the physics practicals with teachers, in school and by email, so I have a few resources to point to.

There is a dedicated TalkPhysics group for the GCSE required practicals – obviously just the physics ones. It’s fairly quiet at the moment, but I/we would love to see more teachers on there swapping ideas and answers, for example about specific components for I/V graphs or precise methods for using a ripple tank. If you’re not already a member, you can get a free login in a day or so, and the group is open to all. Technicians and all teachers of physics – not just physics specialists – are welcome. Please join in.

Most equipment issues I’ve heard about have been predictable:

  • Getting a class around a ripple tank is hard. Much of the work can be done in pairs by putting a piece of laminated squared paper in a Gratnells tray – other trays are available – adding a centimetre of water with a couple of drops of ink, then making and timing ripples. Very fast, very cheap, and lots of data to criticise.
  • Dataloggers for a=F/m. As you might expect, manufacturers are trying to log complete systems which will work brilliantly for a week then be a pain to set-up and calibrate. If you can use phones in school, kids can probably use slow-motion cameras to collect some useful data. Alternatively, I’m a huge fan (no commision, sadly) of the Bee Spi V lightgate. It displays either speed or acceleration of an object passing through it. It doesn’t log it, which to my mind is an advantage as it means kids have to do the table/points/line bit themselves. They’re £20 each, run on batteries and don’t need to be plugged into any device.
  • The specific heat capacity practical – assuming you have the kit – has always produced data with, shall we say, lots to comment on. An improved method is available from PracticalPhysics, and it’s easier if you can (a) use a joulemeter and (b)record the maximum temperature, not the temperature at the end of the heating time.

How are you developing knowledge of practical work and investigations in your teaching ready for the examinations? 

‘Required Practicals’ is one of the sessions I run in schools as part of my day job with the IOP. So allow me to invite you to a virtual session, which will require you to imagine all the hands-on sections. There are presenter notes with even more links than in the slides themselves. PNCs will often run their own versions of these, and we do a lot at days and events open to all teachers. Please consider this an invitation.

If in doubt, checking out the work of Ian Abrahams is always worthwhile. He’s got a book out with Michael Reiss fairly recently: Enhancing Learning with Effective Practical Science 11-16, which I will buy as soon as my next freelance cheque arrives. Unless anyone would like me to review it, hint hint. He writes regularly in SSR so you’ve probably experienced a flavour of his work already.

A few years ago, Demo: The Movie was unleashed on an unsuspecting world by @alomshaha and co. It should be required watching for all science teachers and departments, and provides some great ideas about how to make demonstrations much better for learning. He’s got loads of films, some of which aren’t directly relevant but the techniques discussed are great. I reflected on some of the material in a blog post too.

Other resources I’d recommend (there will undoubtedly be some overlap) are collated at STEM Learning (the eLibrary that was, once upon a time). And I always like to put in a word for the SchoolPhysics materials by Keith Gibb, author of the Resourceful Physics Teacher.

Something I’ve chatted about in workshops, on Twitter and elsewhere; you may find it useful to break down the POE approach in a slightly more specific way which I call PRODMEE:

  • Predict: what do you think will happen? (encourage specific changes to specific variables)
  • Reason: why do you think that? (from other science content, other subjects, life experience)
  • Observe: what actually happens? (we may need to ensure they’re looking the right way)
  • Describe: in words, what happened? (qualitative results)
  • Measure: in numbers, what happened? (quantitative results, devices, accuracy/precision, units)
  • Explain: what’s the pattern and does it match the prediction? (digging into the mechanism)
  • Extend: why does this matter? (other contexts, consequences for everyday life)

What resources or advice can you share with other teachers about approaching a specific required practical? What issues and opportunities have you come across when going about teaching the required practicals to your classes?

A few suggestions I’ve made in workshops, often based on conversations with teachers; this is obviously an incomplete list!

  • Density is boring; why not provide a few blobs of blue-tac and have kids plot mass against volume on a graph. Make it more challenging by hiding a ball bearing inside one to provide an anomaly to the line of best-fit. Or can students separate LEGO, Mega-Bloks etc based on density?
  • Hooke’s Law: as the kids have already seen it, why not try using strawberry laces? Alternatively, there’s a simple set-up using copper wire from PracticalPhysics. And you can always use it to hammer home the idea of science-specific vocab, because ‘elastic’ bands aren’t elastic.
  • Acceleration: I mentioned Bee Spi V for measuring earlier. My only other suggestion is to always teach it as F/m=a so you start with the cause (force), shared out because of the conditions (mass) which leads to a consequence (acceleration).
  • Ripples: discussed above, but you can also use a speaker as a vibration generator for some interesting results.
  • Heat capacity: An old experiment uses lead shot which falls a known distance and heats up. Like stroking a metal lump with a hammer, this is a nice example of the idea that the energy in a thermal store can increase without ‘heating’ as we might normally consider it.
  • I/V characteristics are a lot more interesting if students must compare results from a mystery component to standard graphs. This is included in the presentation of my workshop, linked above.
  • Resistance, series and parallel: instead of just reusing the old ISA hardware, why not try taking measurements of different versions of squishy circuits dough?

 

 

 

 

Energy Language Thoughts Part 4

Parts 1 (Introduction), 2 (Pathways/Processes) and 3 (Stores) are all available and will help make this more useful. Please continue to comment, on whichever post seems most relevant, if you’ve any queries or suggestions. Thanks to those who have already done so.

Practical Approaches

stores-or-pathways

The IOP guidance begins by taking snapshots before and after an event and describing the changes to various possible associated stores. The alternative is to think about the physical processes – which will be variably familiar to students, depending on age – and thinking about the effect they have on parts of the system. YMMV.

The famous energy circus can be used, but be cautious! Some make much clearer examples than others. In most cases you will need to be very specific about the start and end points you wish the students to consider. I recommend checking out the SPT guidance. In particular, the ‘one step at a time’ diagram shows why chains of energy can cause problems. The suggestion there, which I endorse, is that you:

  1. start with the idea of fuels ie chemical stores
  2. make clear that fuels limit effects, they don’t by themselves cause the effects
  3. give high, hot and stretched objects as equivalents, but as they’re clearly not fuels we associate them with
  4. gravitational, thermal and elastic stores respectively

Explained at SPT

I’d suggest looking at your energy circus for clear demonstrations of these to begin with. Next would come a kinetic store, probably as an endpoint. A gyroscope or Newton’s cradle is a nice example of a kinetic store which lasts long enough to be plausible.

Approaches to consider

You could have a first round to develop some basic ideas, then a second with more complex snapshots (either more than one store involved at the end, or the same kind of store but associated with different objects).

Have students identify just the stores to begin with, discuss them as a class, then come back and add descriptions for the processes. This could be split between lessons; that way you can provide correct stores in the second lesson and concentrate on processes. In some cases, such as the classic filament bulb, two similar pathways will be needed.

  • From: thermal store of filament
  • Via: heating by visible radiation, heating by IR radiation
  • To: thermal store of air in the room

If you want them, here are energy-circus-cards as pdf (includes example and blank cards)

Provide sets of laminated cards with stores, and arrows for the descriptions of processes. Labelled arrows are of course an option, but be aware of limitations and I’d include some blanks.

Again, cards-for-energy-v3 as pdf to save you a few minutes.

An extension could be to suggest measuring equipment and/or units for the relevant stores in each situation. If returning to these examples at GCSE, then recall of the equations are the natural next step.

Consider including actual photographs for some situations that cannot be easily reproduced in the lab; this would be a good way to introduce some examples from biology and chemistry. A food chain in biology might, for example, be described so:

  • From: chemical store of lettuce
  • To: chemical store of rabbit

Then

  • From: chemical store of rabbit
  • To: thermal store of rabbit, kinetic store of rabbit, chemical store of fox

And finally

  • From: thermal store of rabbit, kinetic store of rabbit
  • To: thermal store of air

For chemistry, exothermic reactions will involve heating by particles and/or heating by radiation pathways. If the material explodes (which in my experience is the preferred result) then there is some kind of mechanical working too, yes? Be prepared for questions about state changes; the best approach is that latent heat means the thermal store is not only identified by the temperature change. Which, yes, is a complication.

It’s probably worth adding notes – mental or otherwise – to the other science topics so you can remind students of the new language. If you have particular queries, drop me a line in the comments or, for a more considered answer, join in with the discussions on TalkPhysics.

This seems like a good chance to consider the Big Ideas in Science Education. Which should be up anyway, somewhere, but it’s always nice to have a reminder.

Exams and Textbooks

This is where I must admit defeat. I know – in fact I started the first post in this series with this point – that teachers want to know what will get marks and what won’t when it comes to the exams. Sadly, I don’t know. At least one board used the old language in the sample papers originally made available. The list of stores is not consistent between boards, though I hope that makes more sense after Part 3. And so on.

I’m sure we’ll all be happier once we see more examples of possible questions, but I’m not involved much with the boards so I have no insight. My advice – which isn’t official IOP guidance, nor is it specially informed – is that if your students can explain the mechanisms behind the transfers, they shouldn’t need to worry about the language, either pathways or processes. For the stores, it’s probably more important that they can identify the equations that are relevant and be able to do the maths – that, of course, hasn’t changed! I’ve recently discovered that Richard Boohan is putting together some materials; I shall be watching with interest.

Whether students will be penalised for talking about light energy, sound energy, electrical energy – that I don’t know. I also don’t know how much emphasis will be placed on this language by those marking biology and chemistry questions. So I’m not much good, really. Sorry!

Last appeal for comments, feedback, criticism… please let me know what you think of these four pieces. At well over 3000 words I appear to have accidentally written an essay. I hope that if you’ve waded through it, you feel it was worth your time. Please do give me a shout if there’s something I can do to improve the time spent vs time saved ratio.

Energy Language Thoughts Part 3

As you would expect, this follows on from Part 1 (Introduction and Summary) and Part 2 (Pathways/Processes). Even if you’ve read them, you might want to look back at the comments readers have made  – many thanks to everyone who has been able to take the time.

Descriptions vs Labels: Stores

The stores are not simply renamed ‘energy types’. A lot of them use similar words, but that’s because they’re trying to describe the same physics. They represent the changing properties of a part of the system, caused by it gaining or losing energy. When a steel block undergoes physical processes, it changes in a measurable way. It might change shape. Its temperature might change. It might be moved away from the Earth’s surface. It is a shame that exam boards are taking different approaches, but the eight suggested by the IOP are:

  • chemical store
  • thermal store
  • kinetic store
  • gravitational store
  • elastic store
  • nuclear store
  • vibration store
  • electric-magnetic store

More details at SPT

Like the processes, there are sometimes more than one way to consider what is happening. If a gas is heated, the change could be considered in terms of the measured temperature change (thermal store), or in the increased movement of the particles (kinetic store). Realistically, there are not many situations where two stores will seem equally appropriate. And when they are, this is actually a strength. The two approaches will give values for the energy change which are the same. Energy is energy, whether it is considered in the context of a thermal or kinetic store. The whole point of using energy as a ‘common currency’ is that is translates between contexts.

The stores, as discussed in my introductory post, are each a way of considering a physical measurement and an associated equation. The idea is that you consider the ‘before’ and after’ situations for relevant stores, as snapshots. (The exception, for school-age students at least, is a chemical store where the values are found empirically.) I produced, based on some ideas from IOP colleagues, some energy store ‘bookmarks’ which bring together the different aspects. They wouldn’t take long to put together, but you’re welcome to my version:

stores-bookmarks as pdf

Common Variations

The vibration store can be considered as a kinetic store which oscillates. The easier measurement is not speed but amplitude and time period. Imagine trying to find a meaningful value of the speed of a swinging pendulum, for example. But some boards are omitting it, which is fairly easy to justify.

I’m less happy that at least one exam board (AQA) miss out the nuclear store entirely. This seems like a huge mistake to me as it uses the one equation pretty much everyone knows from physics, E = mc2! It would also make it impossible to start with the sun, which makes most biology a bit tricky. (From nuclear store via particle heating processes to sun’s thermal store then via radiating processes to Earth’s thermal store and biomass chemical store)

The electric-magnetic store – not electromagnetic – is about the position of objects within two kinds of field. Now, I know they’re related – Maxwell’s equations and all that – but I think for most students it’s a lot easier to consider two separate stores, the magnetic and the electrostatic. The upside is that this means you can clearly link them to gravitational stores and so cover fields as a ‘meta-model’. The downside is that it makes the stores list look even more similar to the old approach. If you take this tack, make sure you emphasize that it’s an electrostatic store to clearly distinguish from the electric current pathway.

Which brings me to…

What about light/sound/electricity?

The SPT resources have some very good explanations on this. My reasoning is that they are processes which only have meaning if we think about duration. To describe them in numbers, we use power in Watts rather than energy in Joules. So they are, obviously, real physics effects. But they fit best into this model as processes shifting energy between stores, rather than stores themselves.

Disclosure: my issue with this is that a very strict interpreation of thi would seem to rule out kinetic stores as well. The snapshot approach – comparing the change to stores in between two static frames – makes it hard to reconcile a moving object with a single instant. Hmm. Although we have no problem with considering momentum at a moment in time, yes? Contrariwise, students may have an image of light as being made up of photons as moving objects, or when older the equation E=hf. Hmm again. And what about latent heat? This is best considered as a special term of the thermal store, but it’s not obvious. (Thanks to my colleague Lawrence Cattermole for reminding me of this today.) Of course, no model is perfect. The test is whether this approach is better than the ‘types’ of energy approach that has been so pervasive.

‘Better’, of course, is not a very scientific term! It is more accurate when describing the physical processes. The words are a closer narrative match to the equations students will need to use as they develop their physics. The model is different to what we and our students are used to, but objecting to it on that basis seems short-sighted. As I originally said, you could argue that the timing is unfortunate, with new specs and grading systems, but I don’t think we’d ever be at the point where all science teachers welcomed a change with open arms.

As always – please comment, respond, shout angrily at me using the field below.

Energy Language Thoughts Part 2

The previous post was a summary or introduction – thanks to all those who have commented already – and tomorrow I’ll be moving on to stores in more detail. But for now…

Descriptions vs Labels: Processes

To make life easier, humans like to use shorthand for complex processes. These are categories or labels, not detailed descriptions. Many pathways or processes can be put into one of these categories, but the aim should always be end up able to describe what is actually happening.

  • Heating by particles
  • Radiating (aka heating by radiation)
  • Electrical working
  • Mechanical working

Longer explanation at SPT

How we choose these categories will alter our interpretation. For example, are sound waves a form of mechanical working? Or do we include all waves in the ‘radiating’ category? The physics description of what is happening is what we and our students should be concentrating on, because it doesn’t change. The ideas about Johnstone’s Triangle that I’ve read about via Michael Seery’s blog, from chemistry education, has obvious parallels.

johnstones-triangle-1024x573

Reproduced from Michael’s post, credited to University of Iowa.

If we can link the macro (observations in lab) and sub-micro (particles and interactions) levels, the symbolic can wait. A similar discussion is had on SPT about alternating between the lived in world and a theoretical model.

Avoiding using these categories – which by their very nature are imprecise – might be worth considering. It would be very easy for students to think they have to assign any physics process to one of the four listed above, without really thinking through what’s happening. (If you’d like to consider symbolic approaches, I’d suggest checking out the physical versions of energy bar charts as described here by Greg Jacobs.)

As pointed out by several – most recently Richard Needham on Twitter – changing how energy is described in physics lessons means nothing if we can’t apply this to biology and chemistry. And it needs to make more sense there too! In school chemistry, heating and radiating (in the form of light-emitting) will be the significant processes. The equations used later on for enthalpy change – endo and exo-thermic reactions and so on – work nicely with this framework. In school biology, the transfer of energy is usually about photosynthesis (a radiating pathway fills a chemical store by the production of glucose/oxygen) or nutrition/metabolism. (More about stores in the next ‘chapter’.) One of my jobs is to have a closer look at the KS3 specification for any mention of energy in chemistry and biology and see what I’ve missed – please let me know in the comments if this has been done already!

I’ve heard – and contributed to – discussions about other possible pathways, perhaps useful for younger students. The regular suggestion is reacting, which would include chemical reactions in cells (aka metabolic-ing) as well as the lab. The shift happens between two chemical stores. The physics process, if we look closely enough, is about electron exchange between atoms. But I wouldn’t want to have that level of explanation in a year 7 lesson! As ever, the question is about us choosing a realistic level of detail for our students at any particular time.

The Power of Processes

I wrote earlier that we weren’t interested in how quickly a process worked. That’s obviously not always true; rates are very important in physics! So the process can happen quickly or slowly, which changes the magnitude of the final change in the relevant stores. This tells us that processes are about power, not just energy. (Thanks to Brendan Ickringill who pointed out the word rate is important.) The analogy I use is that of the carbon cycle. Asking how much carbon is ‘in’ plant biomass at any point is a meaningful question, if not an easy one. But it makes no sense to ask how much carbon is ‘in’ combustion, or any other process. They are rates, not amounts.

My colleague Trevor Plant reminded me of the need to change how we use Sankey diagrams for this new approach. The width of the arrow can now describe the power of the process, transferring or shifting energy between stores. A lot of the same questions could be asked, and efficiency is still a helpful consideration. We’d now think about useful processes (with values in watts) and wasteful or dissipative ones. As ever, we’d need to distinguish between similar processes; for example, energy shifted to the thermal store of water in a kettle is useful, whereas heating of the air around it is not.

Effectively what we’re doing here is describing what the ‘magical arrow of energy transfer’ is symbolising. A useful resource is a set of laminated arrows which students can write on for descriptions of the physical processes. You could provide some with descriptions on them, but the danger is that the class – or the loudest member of it – will then choose a best-fit rather than something more accurate. If you also supply laminated cards – as boxes, not arrows – with the eight stores on them, they are ‘encouraged’ towards the new model. These might be particularly useful to analyse a chosen selection from the famous energy circus.

On this theme, I produced some cards to go on the electrical sockets in the lab. The idea is to remind students that the current comes from somewhere else, and that the electrical supply is a pathway/process, not a store. Download below.

power-stations as pdf

As before, I hope the discussion here is useful – and please respond in comments if there’s something I’m missing out! Next post will be looking at stores in more detail, then hopefully a last one at the weekend on practical approaches and ways to adapt what you used to use!