DIDATTICA DELLA CHIMICA E TRASPOSIZIONE DIDATTICA Parte seconda - Un’approccio didattico alla costruzione del concetto di trasformazione chimica
2016
Ghibaudi, Elena | Roletto, Ezio | Regis, Alberto
In the second part of this work, we present an example of didactic transposition carried out in Italy, with high school students. The educational activity is focused on the concepts of chemical transformation, chemical reaction and reaction equation; an achievement of this activity is the introduction of the distinct concepts of atom and molecule by the students themselves, as a hypothesis that allows interpreting the observed phenomenology. This sequence is conceived according to a historical–epistemological approach and it is based on a socio-constructivist praxis. It relies on the problem-situation as a didactic tool. In the first part of this article, we describe the activities that drive students to elaborate the concept of chemical transformation based on the concept of ‘identity of a chemical substance’, and the use of the particle model. In the second part, we describe some learning activities that lead students toward the Avogadro's hypothesis and Cannizzaro's distinction between atoms and molecules, starting from the contrast between Dalton's and Gay-Lussac's positions.
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