This paper is concerned with the study of the argumentation of eight to ten years old students in a physical knowledge class. The analysis was carried out from the structural point of view, through the identification of the components present in isolated arguments, as well as looking for different ideas and searching for syntheses in the argumentation as a whole. It was also observed in which way the teacher conducted the discussion and a IRF discursive standard mainly elucidative was identified. This kind of discourse provided a cooperative space for the externalization of ideas, which allowed at the same time the respect for alternative explanations and the selfconfidence regarding of complementary arguments. Besides presenting many statements in their justifications, relating them to the data they gathered, students stated hypotheses from their conclusions and the proposed problem stimulated them not only to solve it but to try alternative solutions as well.