Preservice teachers' pedagogical content knowledge of using particle models in teaching chemistry

In this article, we describe the results of a study of the pedagogical content knowledge (PCK) of preservice chemistry teachers in the context of a postgraduate teacher education program. A group of preservice teachers (n = 12) took part in an experimental introductory course module about the use of particle models to help secondary school students understand the relationship between phenomena (e.g., properties of substances, physical and chemical processes) and corpuscular entities (e.g., atoms, molecules, ions). The module emphasized learning from teaching by connecting authentic teaching experiences with institutional workshops. Research data were obtained from answers to written assignments, transcripts of workshop discussions, and reflective lesson reports, written by the participants. The outcomes of the study revealed that, initially, all participants were able to describe specific learning difficulties, such as problems secondary school students have in relating the properties of substances to characteristics of the constituent particles. Also, at this stage, all preservice teachers acknowledged the potential importance of using models of molecules and atoms to promote secondary school students' understanding of the relationship between phenomena and corpuscular entities. After teaching, all preservice teachers demonstrated a deeper understanding of their students' problems with the use of particle models. In addition, about half of the participants had become more aware of the possibilities and limitations of using particle models in specific teaching situations. Through learning from teaching, the preservice teachers further developed their PCK of using particle models, although this development varied among preservice teachers studied. © 2005 Wiley Periodicals, Inc. J Res Sci Teach 42: 947–964, 2005