Abstract

Some teachers perceive radioactivity as a difficult topic to teach due to its abstract nature. This topic is included in Lesotho at the senior secondary level in the combined science syllabus. This paper reports on some findings of a larger study which was carried out to make explicit two teachers’ pedagogical content knowledge (PCK) on teaching radioactivity, and to investigate the role of experience in the development of PCK. Two teachers participated in the study: Mr. Victor who had 19 years experience and Ms. Grace who had 3 years of teaching experience at the time of the study. The paper focuses on the use of content representation (CoRe), a tool which was employed in this study to portray the teachers’ PCK. The results reflected by the CoRe indicate that Mr. Victor and Ms. Grace had some common views towards the teaching of radioactivity, but they also had differences in the way they conceptualized the teaching of this topic. The evident differences were on the content each teacher intended to teach, difficulties associated with the teaching of this topic, knowledge about students' factors that influence the teaching, and some teaching strategies the teachers employed. Mr. Victor showed greater awareness of learning difficulties than Ms. Grace and this could be linked to his level of experience, as he might have encountered some of these difficulties in his years of teaching. The CoRe was found to be a valuable tool for articulating the teachers’ PCK.