This study examined the factors that influenced secondary school chemistry teacher candidates' choices of instructional methods in the context of "separation of mixtures" topic. The participants were six senior pre-service chemistry teachers following the Teaching Experience Course. Semi-structured interviews, lesson plans, participants' reflections on their teaching and observation of participants' instruction on the "separation of mixtures" were the data gathering instruments. Qualitative analysis showed that various factors affected pre-service teachers' teaching decisions. Among these factors were mentors, students, the topic taught, general pedagogical knowledge, own learning styles, subject matter knowledge, concerns about classroom management, and availability of materials.