In this article the 'lesson preparation method' was used to investigate pre-service teachers' pedagogical content knowledge, in particular their knowledge of pupils' conceptual difficulties on temperature and heat. A relation is found between the conceptual difficulties they themselves have or have had. The discussion considers what pedagogical content knowledge teacher educators should include in the initial or inservice teacher education curriculum.Dans cet article, la "méthode de planification de leçons" a été utilisée pour effectuer une recherche sur la connaissance pédagogique de contenu chez de futurs enseignants, en particulier sur la connaissance qu'ils ont des difficultés conceptuelles des élèves quant aux concepts de température e...