Investigating students' and teachers' reactions to a curriculum on the evolution of a chemical system

A curriculum on the evolution of a chemical system was recently implemented in the final year of Higher Secondary Education (grade 12) in France. An analysis of the students’ reasoning and difficulties when solving problems on the evolution of a chemical system is presented according to two axes, an epistemological one based on the structure of scientific knowledge and a psycho-cognitive one taking into account alternative conceptions. The curriculum includes two approaches, a thermodynamic one which provides a systematic procedure to predict and justify the direction of chemical changes and a kinetic one, which aims at explaining the dynamic nature of the chemical equilibrium state. Questionnaires were given to the students, where they were asked to predict or justify an evolution or a lack of evolution. The analysis of their answers revealed difficulties in establishing a proper link between the model level and the empirical level in some precise situations, a persistence of previous models of chemical changes and a nearly complete lack of use of the kinetic model.