The « amount of substance » and its unit the « mole »

International audience; The ‘‘amount of substance’’ and its unit the ‘mole’ are concepts that have been a frequent subject of discussion among science education researchers. These concepts present difficulties to students and teachers. The attempt to make two incompatible paradigms, the equivalentist and the atomistic paradigm, converge helped the scientific community to reach agreement on what the word “mole” actually means. However, the consequences of the convergence were that multiple meanings and conceptual contradictions resulting from the historical evolution of the mole have become sedimented in the SI definition of the mole. I’m interested about the way the mole concept is presented in classrooms. I used for this pilot study two videos of two teachers presenting the amount of substance and the mole in their classes. They use the same teaching sequence and they give to students a document with a summary of the knowledge to be learned designed and improved by the SESAME group. In one hand, the analysis of the summary document is based on the semantic mistakes. In the other hand, based on the concept map linking idea were searched in the postlab session. The analysis shows that the summary document uses the correct expression. The analysis of videos shows that the mole concept was defined with emphasis on the mole as a number. Neither the SI definition in terms of 12 grams of 12C nor the connection between molar mass and relative atomic mass was explicitly explained. As suggested by Fang (2011) because of the differences in how the mole concept has been conceptualized between the scientific and the educational domains, through their training, teachers learn to use the mole concept as a ‘tool’. This content analysis formed a part of a project that will investigate the process of teaching and learning the mole concept in secondary classrooms.