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.

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