A long-term study of students' explanations of transformations of matter

We report on a long-term study of young children's understanding of matter and its transformations. Interviews concerning children's conceptions could be seen in the idioms, personal framings of experiences, that became apparent as a result of the longitudinal design of the study. As part of the project, we also made an early (at the age of 6) introduction ot the concept, molecule. Depending on the phenomenon presented to them for explanation, some of the children used the molecule concept as a tool for understanding and explaining, while others did not. By focusing on a few examples, which we analyse in detail, we argue that long-term studies give rich detail and important information about children's learning that other kinds of study do not.