Cooperative learning and inquiry-based pedagogies often present a new paradigm for science teachers in which their traditional role as expert content givers shifts to one of facilitation and coaching. Previous research on these pedagogies in chemistry mainly focused on the structure of the curriculum materials used with these pedagogies and their impact on student achievement. What remains largely unexplored is the nature of teacher's moves when dialoging with student groups or leading whole class discussions. This study examined the role of teacher-initiated discourses in developing students' representational fluency with respect to the topic of dissolved ionic compounds in water. Two kinds of teacher-initiated discourse were observed: monologic and dialogic discourse. We describe the nature of these discourses and their impact on student understanding of dissolution processes. We particularly describe certain teacher moves that were found to be more helpful than others when facilitating students' representational fluency in chemistry.