Models from history to the classroom: an historic-epistemological approach to chemistry teaching

Far from being presented as a main epistemological obstacle, the discontinuous nature of matter is usually taken for granted in chemistry teaching and the atomic hypothesis is reduced to a mere conceptual instrument that provides an interpretation - at the microscopic level - of Proust’s empirical law of the definite proportions. In this paper we will show an example of how the history of chemistry can be exploited as a source of problematic questions aimed at driving students towards the elaboration of a molecular/atomic model of matter. In particular, a teaching sequence focused on the discussion of the experimental results by Gay Lussac on the reaction between gaseous substances, may lead students to formulate the existence of atoms and molecules as a necessary hypothesis to explain the experimental findings, through a spontaneous evolution from Dalton’s particle model to Avogadro’s hypothesis.