University York U.K.
This chapter draws attention to two quite different kinds of teaching and learning issues. The first concerns the difficulties which many learners have in coming to terms with the scientific understanding of thermal phenomena. The second is the challenge posed by reasoning about situations where more than one factor simultaneously influences an outcome, with a set of interrelated effects happening together and not in sequence.
The research evidence for students' difficulties in grasping the scientific view of temperature, heat, and internal energy is considerable. Researchers' findings echo the more informal observations of teachers in the classroom. Perhaps the principal value of research is to draw attention to the basic ideas which learners appear to struggle with, yet which can appear so obvious to the teacher that they may not be explicitly taught at all. We need to be reminded that younger students need to be helped to understand that all materials, if left for long enough in a fixed temperature environment, reach the temperature of that environment, regardless of the material they are made from; that they need to be taught that the temperature of all materials can be raised by heating them; and so on.
Basic thermodynamics is, however, one of those topics where the number of articles in the science education literature about learners' difficulties is matched by those arguing that the treatment in many textbooks is inaccurate and at odds with the actual scientific understanding of the topic. In particular the use of the noun 'heat' has been questioned, with some suggesting that we should always talk instead of the process of 'heating'. Viennot's discussion in the opening pages of this chapter outlines the scientific view of thermal processes, and indicates just how subtle and difficult some of the ideas are. Bearing in mind that most of the children in classes learning the basic ideas about temperature and heat will not go on to become physicists, but require instead an understanding of scientific principles which will be of use to them in tackling situations in their everyday lives as citizens, I wonder if an understanding rather closer to the 18th century 'caloric' model of heat might not be a more realistic teaching aim? Appreciating the difference between the intensive quantity, temperature, and the extensive one, heat (or energy), recognising that heat is transferred spontaneously from objects at higher temperature to those at lower temperature, and grasping the role of insulating materials in slowing the rate of this transfer - this is clearly a significant cognitive challenge for many learners. These ideas, however, simplification of the full scientific picture, are useful in understanding many everyday phenomena. Indeed much work by engineers and biologists is based upon them. It is interesting to note that some recent work by science educators takes as its aim the teaching of just this sort of 'pragmatic model' of thermal phenomena (Linn and Songer, 1991).
The second strand of Viennot's chapter deals with an issue which is clearly broader than basic thermodynamics: the forms of reasoning used by students when trying to explain phenomena. The tendency to use 'linear causal reasoning' is likely to be found in many areas of science. It is less easy to see how we might help students to overcome it. One starting point might be to recognise that all of us reason in more sophisticated ways when we are discussing familiar subject matter. When we move to domains where we are less sure of our knowledge, our style of reasoning also becomes more basic. I am inclined to think that the issue here is not students' ability (in a developmental sense) to use more sophisticated patterns reasoning about multivariate systems, but rather their ability (and confidence) to do so when the context is an abstract and unfamiliar one. Helping students develop scientific forms of reasoning may then involve practice in reasoning about more familiar multivariate systems and models drawn from everyday contexts, perhaps reflecting on the forms of reasoning used to draw these out and make them explicit.
Linn, M.C. & Songer,
N.B. (1991). Teaching thermodynamics to middle school students: What
are the appropriate cognitive demands? Journal of Research in Science
Teaching, 28 (10), 885-918.
SectionC, Comments on
C3 from: Connecting Research in Physics Education with
An I.C.P.E. Book © International Commission on Physics Education 1997,1998
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