Relationships between everyday knowledge and scientific knowledge: understanding how matter changes

This paper analyses the representations held by adolescents and university students in relation to the mechanism for explaining changes in matter (changes of state, dissolutions, expansions and chemical reactions) in terms of the kinetic theory. The answers to a questionnaire were analysed by considering the proportion of correct answers and the use of alternative conceptions. The results show that understanding of explanatory mechanisms of changes in matter is affected by age and instruction level and content of the problem. The main conception that competes with the kinetic model is the attribution to the particles of the changes observed, at a macroscopic level. This is more evident in changes of state and expansions than in other changes. This confusion results from a failure to differentiate properly between the represented reality and the model that represents it. In conclusion, analysis has shown once more students' difficulties in going beyond apparent reality or integrating the data obtained from it into the scientific models they learn at school.