CHANGING PUPILS’ CONCEPTIONS ABOUT WEIGHT APPLYING VARIATION THEORY

In phenomenography the aim is to describe and classify people's conceptions. Teachers have to be aware of the various alternative conceptions on which pupils are relying in their reasoning when they try to understand a concept or a phenomenon. Marton's variation theory of learning gives guidance to teachers how to design a successful teaching intervention by taking into account discernment, variation and simultaneity. In this article comprehensive school pupils' conceptions on the concept of weight in the pulley surrounding have been studied using phenomenographic method. Pupils from 5th, 7th and 9th grades compared the weight of a small standard mass and a big bag hanging in a pulley at different positions in balance. In all the three age groups the majority (about 70%) of the pupils stated that the lower hanging bag is heavier. From the pupils' justifications five hierarchical categories were found: Motion, Position, Appearance, Material and No reasoning. Only about 5% of the seventh graders and 10% of the ninth graders seem to have an idea about the scientific explanation based on the immobility of the hanging objects. Next, in order to change these conceptions a teaching intervention was planned so that in three successive demonstrations the critical features found in the earlier study about pupils' conceptions were varied. After the teaching about 40% of the fifth graders and 45% of the ninth graders perceived that they have to pay attention to the immobility of the objects. Finally, it is shown how the cognitive conflicts and the four patterns of variation gradually change the pupils' ideas toward the scientific explanation. Teachers can help pupils by using successive demonstrations with appropriate variation and taking up in discussion pupils' misconceptions and the critical features in the demonstration.