Inferring Pedagogical Content Knowledge and Pedagogical Knowledge of two French chemistry Teachers from the Study of their Activity

International audienceThe teacher's activity in the classroom relies upon both the determinants of the teaching learning situation (the students, the content-to-be-taught, the syllabus…) and the teacher's beliefs and knowledge. This study addresses the activity of two teachers working on the same subject, the spontaneous evolution of chemical systems in a 12 th grade form. During a training session aiming to develop the teachers' professional knowledge of this topic (content knowledge, CK and pedagogical content knowledge, PCK), each teacher presented his/her lesson plan and goals before implementing them. Then each teacher watched his/her own classroom video to comment and discuss his/her choices and actions and the students' behaviour. Analysis of the enactment of the lesson plan shows the experienced woman teacher's classroom management offered the students more opportunities to express their reasoning. She could reflect on her students' reasoning and display various types of knowledge by commenting her actions while watching the video: pedagogical knowledge, PK, and knowledge of students' difficulties and knowledge of instructional strategies to overcome these difficulties which are two components of PCK. The less experienced teacher expressed limited professional knowledge (whether CK, pedagogical knowledge, PK or PCK). The discussion will propose some reasons for this