This study investigates pre-service Physical Science teachers’ (n = 110) pedagogical content knowledge (PCK) in integrating the nature of science (NOS) into Chemistry instructional planning at a South African university. The research sought to explore how pre-service teachers incorporated NOS into lesson planning and to identify the challenges they encountered in aligning NOS with Chemistry content. Adopting a qualitative case study design, participants engaged in a six-week intervention involving explicit instruction on NOS through lectures, guided discussions, and reflective activities. They subsequently developed lesson plans integrating NOS within three Chemistry topics: Electrochemistry, Reaction Kinetics, and Chemical Equilibrium. Data comprised 110 lesson plans, which were subjected to qualitative content analysis involving systematic coding, categorization, and interpretation to identify patterns of NOS integration, content selection, and pedagogical approaches. The analysis revealed that, although participants demonstrated partial understanding of NOS, they experienced considerable difficulty embedding NOS meaningfully within their instructional designs. Key challenges included selecting appropriate Chemistry content to illustrate specific NOS tenets, establishing coherent links between NOS and scientific concepts, and designing contextually relevant teaching activities. Reaction Kinetics emerged as the most challenging topic for integration. Frequently addressed NOS tenets included the distinction between observation and inference, the absence of a universal scientific method, and the centrality of observation and experimentation in science. The study concludes that pre-service science teacher education should incorporate sustained, practice-oriented strategies to develop PCK for NOS, with particular emphasis on instructional planning that effectively integrates NOS with disciplinary content. Implications for science teacher education curriculum design are teased out.

Keywords: Pre-service, teachers, nature of science, chemistry, pedagogical content knowledge, instructional planning.