Heat Misconceptions

Like many of us, I’m currently spending the majority of my time helping students prepare for external exams. Because of how science exams now work in secondary school, most of my classes are facing one or more exams in the next few weeks, just for physics. Seven classes are doing GCSE content (2 x Yr9, 3 x Yr10, 2 x Yr11) and two classes are in sixth form.

Something I’ve spent a little time on has been prompted by the variety of answers to mock questions on heat transfer. It was clear that many able students were struggling with clear explanations – and perhaps understanding – of mechanisms of the transfer of thermal energy, as demonstrated by Qs 4 and 5 on the AQA P1 June 2013 paper. So I looked into it.

Examiner’s Reports

My first step was to check whether this was an isolated case or something seen for these exam papers when originally sat. I strongly recommend all colleagues, if they’re not already familiar with it, find where they can read the reports written after the exam for the benefit of teachers and exam boards. They’re available (delayed) for pupils too, but with AQA you need to go through the main subject page rather than to the quick ‘Past Papers’ link.

…nearly half of students scored two marks or less. Common mistakes were referring to ‘heat particles’, thinking that the vacuum stopped all forms of heat transfer, thinking that the vacuum contained air and referring to the transfer of ‘cold’.

…Students who referred to water particles often mistakenly referred to them ‘vibrating more’ as a result of the energy given, or to the particles themselves becoming less dense.

From AQA P1 June 2012 Report

So it wasn’t just my kids.

Now What?

I think of myself as a fairly evidence-based practitioner, so next I wanted to check out some wider sources. A quick search for ‘physics misconceptions heat’ has a large number of results, including one from more than 20 years ago which shows how established the problem is.

As a science teacher, Physics Education from the IOP and School Science Review from the ASE seemed a good place to look. Unfortunately both require memberships, a problem in terms of cost which I’ve blogged about before. Students’ misconceptions about heat transfer mechanisms and elementary kinetic theory is relevant, as is this resource available without login on the ASE site. R Driver’s book Making Sense of Secondary Science was one of several recommended during an #asechat “What misconceptions do students have in science?” in 2011.

I used the students’ answers as a way to diagnose the ‘alternative conceptions’ that they had built up over time. For many these had clearly been established long before my arrival, but I’m going to build some of the ideas into my next cycle of teaching for early intervention. Some of the points from Cyberphysics UK and PhysicsClassroom.com were also useful. What I produced – firstly as a scribbled list, then as a more formal activity, was the ‘Seven Sins of Heat Transfer’. In time I’d like to produce some confidence grids and link these to the diagnostic questions approach as explained at York Science. Concept cartoons with clear viewpoints let students explore different models without ‘owing up’ to ideas they think are wrong, which can be very helpful. And so here’s one of the great @DoTryThisAtHome cartoons:

 

Seven Sins of Heat Transfer

  • Heat rises
  • Particles of heat
  • Expanding particles
  • Shiny materials are good conductors
  • Cold gets in
  • Condensing and contracting are the same
  • Trapped particles can’t move through a vacuum flask

These are what I wrote while marking papers; I’ve just removed the profanity. My reading showed me that some were common alternative conceptions, while others demonstrated a poor understanding of technical terms, often made worse by persistent misuse in ‘everyday’ language. A bit of thinking, and more reading, helped me find ways to highlight these issues for students.

Printable version with prompt Qs: 7sins as .pdf

EDIT: I shouldn’t have needed prompting, but CathN suggested in the comments that model answers would be useful, particularly for non-specialists. And so I’ve put together a presentation going through each of the sections, explained more or less the way I would in class. Obviously colleagues will have their own thoughts and preferred analogies, but I’d love comments on possible improvements; simply click on the title slide below.

7sins

Alternatively: 7sins as .ppt

When time allows during revision, and certainly next time I teach this content, I’ll be linking these misconceptions explicitly with practical activities. I think I’ll also ban the use of ‘heat’ by itself. If students are forced to use ‘collisions between touching particles’, ‘energetic particles in a lower density region’ and ‘thermal radiation’ then we should be able to solve the sloppy language issue, at least.

Thoughts and comments on this very welcome; it strikes me that I could usefully spend time producing a series of lessons and resources on just this sort of thing. Exam question followed by diagnostic questions, circus of activities to highlight misconception, then applications of correct idea to new situation. So if anyone wants to pay me, well, you know where I am…

In the meantime:

I’m trying to track my impact (eg you using this resource or basing your own on my ideas). You don’t have to leave your name, just a few words about how what I did made a difference. If you’ve blogged about it, I’d love for you to include a link. Tweets are transient, comments on the posts are hard to collect together, but this would really help.

Blog Feedback via Google Form

 

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10 thoughts on “Heat Misconceptions”

  1. As a biologist who takes general science at ks3 it would be really useful to be able to tackle rather than unwittingly reinforce misconceptions. Could you possibly provide ideal answers for the diagnostic questions?

    1. Cath
      I’ll see what I can put together – I guess the most useful addition would be a PowerPoint with one slide per answer? Something I should have thought of when I did this, but the original version was for my own use. Thanks for pointing out my omission!

  2. Hi. Thanks for these thoughts, and they may well help students, but in my opinion they are expressed poorly. Just off the top of my head

    You say: In radiation, waves are emitted by hot objects and absorbed by colder ones.

    Actually waves are emitted and absorbed by all objects at all temperatures.

    You say: Cold is the result of a lack of heat energy. If heat moves away (by any method), what is left behind is colder.

    This is not true when materials change phase. If heat is removed from an ice-water mixture at 0 °C the water will change to ice but the temperature will not change

    Additionally I also find the avoidance of discussion of atoms and molecules bewildering. Regarding the AQA report you quote

    “Students who referred to water particles often mistakenly referred to them ‘vibrating more’ as a result of the energy given,”

    Incidentally I have no idea what a ‘water particle’ is. But it is quite correct that water molecules will indeed vibrate more as result of energy given. I think ‘vibrating more’ pretty accurately describes an increased amplitude of vibration.

    All the best

    Michael

    1. Michael

      Thanks for taking the time to comment – sorry I didn’t reply earlier but the arrival of half term left me too tired to do more than approve what you’d typed.

      Your three points are useful – let me deal with them individually.

      You are of course right that everything above absolute zero emits (thermal) radiation. To be more exact, my suggestion for the students should have made clear that I was describing net heat transfer. In the situations they would encounter, only the overall effect would normally be considered. I suppose this is an example of proposing a second misconception while trying to give them a model that helps them overcome the first!

      I’d completely overlooked the concept of state change, and I shouldn’t have done. An interesting discussion to be had with students is the difference between ‘colder’ meaning a lower temperature, and ‘losing heat energy’ which can have two different effects. At the moment latent heat isn’t taught at GCSE which arguably would help by making this distinction numerically.

      I’d have to disagree with your last point. As you say, I was quoting from the AQA document. I actually prefer their wording and make a deliberate choice to talk about ‘particles’ when teaching about heat transfer, as this allows students to focus on the mechanism rather than the details of the substance. ‘Particles’ is, I would argue, inexact rather than wrong. It means students don’t get mixed up when discussing what goes on in metals (atoms/ions) compared to non-metals (molecules). I teach students to focus on better wording than ‘vibrating more’ as this causes problems later on, for example in sound waves, the distinction between ‘vibrating faster’ and ‘vibrating with higher amplitude’ is important.

      1. I demur. Particle is a completely general term from the english ‘part’ and the participle ‘idle’ meaning small. It gives no unifying conception of the structure of matter. Atoms are profoundly and significantly >identical< and inconceivably tiny. Using the correct words is extremely important for building a wider conception of our theories of matter, for linking with chemistry and biology, and for just general cultural relevance. The avoidance of using the words atoms and or molecules is (IMHO) bizarre. Incidentally I speak as a parent of child taking GCSE sciences at the moment. He has to get the ideas – and then dumb them down for GCSE examiners in order to get the marks. How bonkers is that!

      2. Of course I – and I’m sure colleagues – use the terms, and I hope correctly. But with students who have a range of abilities, it is often important to choose which aspect we will focus on at any one time. A student who used ‘atoms’ in a question about water molecules being heated might lose the mark, even though they clearly explained the mechanism of convection. By using particles this can be avoided.

        Surely in convection, or state changes, what matters is the movement of particles, not whether they are atoms or molecules? By using the more general term I have found students find it easier to extend their mental model to other examples.

        As for your son, he should never lose marks for (correctly) using more advanced language or ideas than specified in the markscheme. I normally advise my more able students that the only problem is to do that well in the time available.

  3. What a lovely blog (I’ve just stumbled in from Google and will be keenly watching you in future). I’ve always struggled figuring out exactly where my pupils go wrong on all sorts of concepts. I still remember one of my ‘epic teaching fails’ from 5 years ago where a pupil left my care after 2 years in my class still believing ‘we live IN the Earth’ and nothing I could think of would convince her otherwise! I tend to use Concept Cartoons and try my best to make up my own. The snowman in a coat (will he melt or not?) is a favourite of mine for this topic area.
    The comment added perviously to mine by Michael has made me smile in 2 ways; firstly I love that despite being educators we ALL make minor mistakes and secondly I love that people want to help and will add comments. Michael – do you have a Science teaching blog I can follow?
    I’ve stored your ‘no no’ list at the bottom of my heat transfer revision Powerpoint and will edit it in and use when I come to the topic next year. Thank you.

    1. Really pleased you found the post and comments useful – that’s the whole idea! It’s certainly true that blogging helps me clarify my ideas, sometimes as I type and sometimes via helpful comments such as Michael’s. If you have as moment I’d really appreciate an addition to the Google form, link in the post and in the PowerPoint.

      You can subscribe for emails or via rss to keep up with my writing.

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