Teaching chemical change modeling to Tunisian students: an “expanded chemistry triplet” for analyzing teachers' discourse

Through a comparative analysis of the chemical content of three teachers' discourse; we propose to give answers to the question: “how is the connection between the experiential level and the generally accepted representation of the three levels of chemistry presented by teachers to Tunisian students, during their first contact with chemical change modeling”. We chose to perform the analysis using an “expanded chemistry triplet” to represent the different levels and their possible connections to the elements of knowledge taught. These elements of knowledge, called facets, included definitions, representations and rules used by the teachers to convey the meaning. While there was some difference in priorities between the three teachers with regard to teaching content, the connection between the experiential field and the three levels of representation of chemistry was only partially taught by all. It is the description, the interpretation and the representation of objects and events of the experiential field at the macroscopic level that are strongly in the majority. On the other hand, interest in the sub-microscopic level and clarification of the procedures to implement for the quantitative treatment of chemical reactions seems insufficient. The responsibility is thus left to the students to acquire a large amount of knowledge and expertise. These observations led us to formulate proposals for improving the teaching of chemical reactions and teacher training.