Rôle de l'enseignant dans deux séquences d'enseignement fondées sur l'investigation: la flottabilité en classe de cinquième

The purpose of this study is to investigate the impact of an explicit hypothesis writing stage on the teacher's management of a debate stage, while a course about buoyanci in secondary school. This work takes on socio-constructivist approach in order to study the activity of the teacher and the students. The video data analysis of the didactic engineering have been recorded with the software Kronos. Our results show a more important student's speaking time during the debate when they have written hypothesis before. And this difference occurs differently according to the themes reached during the debate.