DIFFICULTIES IN ACQUIRING THEORETICAL CONCEPTS: A CASE OF HIGH-SCHOOL CHEMISTRY

Introduction Great difficulties in understanding theoretical scientific concepts have been determined in different areas, including chemistry (Driver, Squirer, Rushworth, & Wood-Robinson 1995, Garnett, Garnett, & Hackling 1995, Griffiths 1994, Pozo, Gomez, & Sanz 1999, Stavy 1995). As empirical studies have shown, pupils develop synthetic conceptions that often describe microscopic processes in terms of perceptual macroscopic entities. Pupils believe that copper molecules melt when copper melts, that atoms have the colour of their substance and that they behave like tiny visible things (e.g. either float or sink to the bottom in a solution) (Albanese & Vincentini 1997, Boo 1998, Driver et al. 1995, Griffiths & Preston 1992, Stavy 1995, Valanides 2000). Similarly, instead of thinking that matter consists of particles, pupils think that particles are in the substances like germs or small pieces of material (Renstrom, Andersson, & Marton 1990). It is possible that the reason children are not actually using concepts learned from school explanatively can be clarified with the help of the Vygotskian distinction between everyday and scientific concepts. According to Vygotsky (1934/1997, 1934/1994), everyday concepts develop from concrete perceptible instances when children single out some common salient features of concrete objects while abstracting from others (e.g. water or ice are different everyday concepts). Such concepts are unsystematic and strictly empirical. Scientific concepts, on the contrary, are defined in relation to each other and are connected with referents only indirectly through their integrated syntactic networks--perceptual and other features are here recombined into new, supposedly more informative, structures. For example, from the point of view of chemistry, water and ice are the same substance even if they are not perceptually similar. Scientific concepts are usually formally learned at school (by verbal definitions, models or symbols) and they refer to entities children have not immediately experienced in their lives, and therefore are difficult to make sense of. The structure of chemical science embodies these psychological differences between everyday and scientific thinking extensively. Different configurations of atoms and molecules do not have directly perceptible referents, yet they produce different kinds of perceptible substances and their changes. What chemistry education is trying to achieve, is to set up a cognitive non-perceptual sign-mediated structure in a child's cognitive system which afterwards enables them to predict and explain the whole range of visible changes of substances. Children's initial frameworks, however, are based on everyday concepts. For example, after having observed a needle, a pin, and a coin sinking in water, a child concludes that all small objects sink and begins to use this concept for predicting the behaviour of different objects in water (Karpov & Haywood 1998). The predictive powers of these concepts are, without doubt, narrower and often misleading. In that view, children have difficulties understanding scientific chemistry concepts because they cannot make sense of indirect and abstract chains of new concepts and simply put theoretical microscopic entities, taught in chemistry classes, alongside other perceptible things in the macroscopic world. Microscopic theoretical concepts are taken as new kinds of things one can see or touch, and these are understood in analogy to the everyday macroscopic world. As a result, as far as the explanatory framework is concerned, pupils remain within their initial conceptions, i.e. they think about chemistry in terms of everyday concepts. Hence, scientific concepts are understood as structurally equivalent to everyday concepts; pupils think that microscopic entities also melt, freeze, and evaporate and have colour like real substances (Albanese & Vincentini 1997). …