Impact d'une formation collaborative donnée à des enseignants de chimie du secondaire sur l’enseignement et l’apprentissage du concept de mole

In the absence of epistemological and socio-historical knowledge about the concept of mole and of a relevant didactic transposition of this concept in textbooks, teachers do not have the means to make their teaching as effective as they would like. Several studies confirm that this teaching usually emphasizes the quantitative aspect of this concept, neglects its qualitative aspects and does not always take into account the three areas of knowledge in chemistry: sub-microscopic, macroscopic and symbolic. The socio-historical evolution of the mole is complex. In 1900, Ostwald defined the mole as a "normal mass". In 1961, the mole was recognized as a concept for counting sub-microscopic entities. In 1971, the mole became the unit of the "quantity of substance", however without this being clearly mentioned in the definition. These various definitions leave the teacher puzzled and looking for an adequate definition. In addition, there are many linguistic confusions related to the learning of the mole, such as phonetic confusions (mol and molecule), and symbolic confusions (n, m, M, N, etc.). A teaching of the mole that does not take into account its qualitative and quantitative aspects, the socio-historical evolution of the concept and an avoidance of semantic errors may cause didactic obstacles for secondary school students. Therefore, the general objective of this development research was to study the impact of a training on the concept of mole given to secondary school teachers on the evolution of their professional knowledge and skills and on the reduction of didactic barriers in secondary school students. The training was planned according to a DBR (Design Based Research) cycle which involved numerous interactions between the student-researcher and the six participating teachers from a Lebanese school. This DBR cycle was subdivided into five meso-cycles in each of which the student-researcher conducted developmental activities. The first meso-cycle consisted essentially of a microcycle of analysis and exploration ; the 2nd, 3rd and 4th cycles include microcycles of design of didactic materials as well as microcycles of analysis and exploration, evaluation and reflection ; the last meso-cycle consisted mainly of a microcycle of evaluation and exploration. During the first meso-cycle, an analysis of the data collected during a focus group, an analysis of the preparation documents and a diagnostic assessment of learning confirmed the problem described above. During the following three meso-cycles (2nd, 3rd and 4th), a didactic material was developed and tested in class. Each of these meso-cycles began with a reflexive feedback from the teachers who had experienced the didactic material in class. Subsequently, a synthesis development activity was facilitated by the student-researcher, an improvement of the team material was carried out by the teachers and a test was conducted in class. Each meso-cycle ended with an assessment of the secondary school students’ achievement. During the last meso-cycle, the student-researcher facilitated a focus group and explanatory interviews during which the participating teachers shared their impressions about the effects of the training on their teaching and on student learning. The analysis and interpretation of the results obtained seem to show positive effects on the evolution of teachers' professional knowledge and skills and on the reduction of didactic obstacles for secondary school students. Nevertheless, this research had quite a few limitations, mainly because of the small number of participating teachers.

Keyphrases: Mole, Design Based Research, Didactic obstacles, Professional knowledge