This study investigates the development of Topic-Specific Pedagogical Content Knowledge (TSPCK) of 14 novice uncertified graduate science teachers during a Professional Development Intervention (PDI) on teaching particulate nature of matter. TSPCK was defined in terms of five knowledge components: learner prior knowledge, curricular saliency, representations, what is difficult to teach and conceptual teaching strategies. Data sources consisted of validated pre- and post-TSPCK and content knowledge (CK) tests, teacher-constructed Content Representations (CoRes) before and after teaching and, for four teachers, video-recorded lessons, and field notes together with teacher interviews. The purpose of this study was to investigate how the teachers develop TSPCK through the process. The results provide an insight into how initial construction of CoRes enabled the entire group to start thinking about how to teach the topic. For the four case-study teachers, evidence of TSPCK development was observed in their teaching. These teachers showed greater improvement in TSPCK and CK than those who taught only the prerequisite concepts of the topic. The findings show that it is possible for uncertified teachers to develop PCK in the practice context with appropriate PDI. Some improvement in PCK was also observed for the larger group who taught only prerequisite concepts.