By Marcus Wilson 23/07/2019 4


Hello everyone. It’s been a long while since I was blogging, but I am back again now. The second-half of the year is rather less hectic for me, so I have some time to get back to this.

I’ve been considering recently the learning that students have achieved in our first year paper “Physics in Context”.  This is a paper designed for students who haven’t done a lot of physics. We have collected various bits of data from this paper, and one of the clear messages is the difficulty students find in expressing physical understanding in words. For example, “what do I write down in my lab notebook?” was a question that cropped-up time and time again throughout the course.

It is really difficult for students to articulate their understanding. In some cases, this is because the vocabulary of physics is new, but also because practising physicists use common words in different ways to how they can be used in everyday language. For example, in everyday language we talk about ‘energy’ and ‘power’ interchangeably (as in ‘energy bills’ or ‘power bills’) but they are distinct concepts in physics. But physicists themselves are inconsistent in their usage. While they know what they are talking about, being inconsistent does not help students. In this article, Brookes and Etkina discuss how language affects students’ reasoning about heat in thermodynamics*.

James Joule statue, Manchester Town Hall. Wikimedia Commons.

‘Heat’ is a slipperly thing to grasp. (Actually, Brookes and Etikina suggest that we shouldn’t call it a ‘thing’. More correctly, it is a slippery process to grasp.) That’s not surprising – it took physicists such as Sadi Carnot, Benoit Clapeyron, Rudolph Clausius and James Joule (pictured) and many others collectively about fifty years or so of studying thermodynamics to fully grasp what it was all about. For a long time, the dominant theory of heat was the calorific theory – that ‘heat’ was somehow like a fluid that flowed from one thing to another. A hot object was hot because it had more heat. From a linguistic perspective, ‘heat’ here is being used as a noun. It’s being considered a thing.

Now, this way of thinking actually serves us pretty well for everyday purposes, which is one reason it is very difficult to shift.  When I turn on my electric kettle, the element generates heat and this heat is transferred to the water in the kettle, which gets hot. Right? My heat pump (the very name ‘heat pump’ uses heat as a noun’!) pumps heat from outside to inside. Right?  Well, no. More thermodynamically correctly, ‘heating’ is the process of transferring internal energy from one place to another. ‘To heat’ is a verb. So the heat pump heats the house (correct), and as a consequence the house has more internal energy and a higher temperature, (temperature being a measure of the internal energy per molecule.)

Another reason that it’s difficult to change the ‘heat is a thing’ thinking, is that teachers themselves talk of it in this way, even if they recognize that this is not technically correct. So we say ‘heat’, but deep down we really mean ‘the energy transferred through the process of heating.’ Difficult to grasp? For sure. For many purposes, using ‘heat’ as a noun is a reasonable and indeed even helpful form of thinking. But for many purposes it isn’t, and will lead to confusion, misconceptions and difficulties for students later on in their study. The problem is, argue Brookes and Etkina, how can we possibly expect students to distinguish between these ways of thinking when we are able to jump around between them so freely?:

Novice physics students … have the challenge of navigating expert ways of speaking that must appear ontologically ‘chaotic’ at first.

Many textbooks emphasise that heat is a flow of energy (i.e. ‘to heat’ is a verb) but then go on and use it as a noun. That’s mixed ontology. Confusing?  I’ve done a hurried review of some of my blog entries that I’ve tagged ‘heat’. I’m quietly relieved that mostly I speak of heat correctly (for a physicist) but every so often the noun slips in.

So what should students be writing down in their laboratory notebooks? Brookes and Etikina suggest that students should not be encouraged to use technical terms until they have “established an agreed meaning in the classroom learning community.”  They should be encouraged to write in non-technical terms first, and then, when they are understanding the “how and why”, technical terms should be introduced.

 

*I suspect you will need to pay for this article unless you have access via, for example, a university library.

Reference:  Brookes, D. T. & Etkina, E. (2015). The importance of language in students’ reasoning about heat in thermodynamic processes. International Journal of Science Education, 37:5-6, 759-779.  Note the irony in the title – ‘heat’ is used as a noun.

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4 Responses to “Language in physics teaching”

  • ok, I’ve read your article about why calling heat a thing is wrong, but all I’ve got is confused (oops, done it again, I mean “increased my level of confusion”). I can see that ontologically speaking we could say that the essence of heat is motion, and motion is not a thing so heat is therefore not a noun. Or the concept we label heat is not a noun, so perhaps there is confusion at that level by those insisting that heat can be a noun. But then you’re in prescriptive linguistics and good luck with that, grandad.

    But in a practical sense, most usage of the term ‘heat’ refers to an attribute that if not a noun is at least linguistically noun-like in the same way that bright becomes brightness or hawt becomes hawtness. The lack of quanta doesn’t necessarily mean you have a verb, unless you want the ISO to define hawtness (perhaps the Washington since we have both Kerry and Denzel). But the ISO doesn’t help there since we have Joules or even worse BTUs which are actual heat-as-noun units of measure.

    Perhaps more concrete examples of “heat as a noun hurts us here” and less of all the (apparently much more common) ways that it hurts us?

  • OK, so I’m not a linguist. Brookes and Etkina’s point, however, is that using words in particular ways will influence how students think about the nature of something. In calorific theory (which is incorrect), objects contain a certain amount of heat, which means when one object heats another, heat leaves the first and moves to the second. A consequence of this thinking is that if we start with a sample of gas in a piston at a particular temperature, then do stuff to it in a cyclic way (like increase/decrease the volume, change the pressure etc as in a car engine) until we get back to where we started, with the same amount of gas in the same piston at the same temperature, volume and pressure, then we must conclude that the net heat flow into the gas is zero. Any heat that has flowed in must have flowed out, because the gas is in the same condition it started in. But this is INCORRECT. The calorific theory of heat, as a substance, is not right. There could indeed be a net flow of heat in or out of the gas as it goes around a cycle.

    For many everyday purposes this doesn’t matter, but if you are designing an engine, for example, it certainly does. So the point is that we should not encourage university students to cement their probably-already-held incorrect idea of the calorific theory of heat. And the language by which we talk about heat can lead students towards this incorrect idea if we are not careful.

    So really, my point is, be careful how you talk about things. Incorrect scientific beliefs can be very hard to shift and can become very problematic for students as they continue studying science.

  • First, sorry if the “prescriptive linguistics and good luck with that, grandad” sounded rude, I meant it more as a reference to that practice being a cliche in old people. When you feel a “words mean what I say they mean, not what those youf want” coming on you’re probably about to attempt prescriptive linguistics… and that hasn’t been observed to work*.

    I agree with “be careful how you use words”, I was just struggling to think of cases where the specific example actually hurt. My field is more electronics so I’m well used to “photovoltaic panels produce energy measured in watts” type thinking.

    At first glance your engine example seemed to violate the ideal gas law, but then I realised that the entire point of it is that a heat engine transforms heat into some other form of energy and the ideal gas law isn’t appropriate for describing the complete cycle. Your use of “cycle” to mean ‘open cycle’ perhaps not ideal in this case … but open cycle as a term applied to engines means something different again. To my primitive way of thinking (ie, first year university physics and chemistry) it’s still heat as a lump of energy gets turned into mechanical motion as a lump of energy, and in this case possibly worse some of the disordered motion of the hot fluid gets turned into ordered motion (sans losses because despite our best efforts the second law still applies).

    Perhaps in a way the “heat as noun” is akin to “electric circuits are like water circuits” explanation for how the invisible, intangible electron (if you haven’t seen it, single electron theory is fun) behaves like a fluid? It works 99% and the exceptions can be treated as exceptions. “heat is a thing except that you can turn it into motion, and produce it from …” which are all pretty intuitive at a daily life or even deep history “cave man make fire” sense.

    In conclusion: Words are hard 🙂

    * if you start reading about this be prepared for an exciting detour via etymology, evopsych, and theories of mind as well as deep (human) history because the idea of powerful people controlling language didn’t start with “1984” (the book, not the movie). Or indeed, the Oxford Comma and related ideas about written language.

  • “They should be encouraged to write in non-technical terms first, and then, when they are understanding the “how and why”, technical terms should be introduced.”

    Quite possibly true for other disciplines as well, I think. (Osmosis, I’m looking at you!)