Group talk opportunities in science can be a rich site for conceptual change. The role of the teacher is vital in scaffolding the exploratory talk which can lead children to talk their way to new understandings and clarify their ideas with peers. This study aims to uncover teacher strategies which lead to effective talk for developing scientific understanding. The findings of this small-scale ethnographic case study suggest that the temporal organisation, the way in which the teacher organises the timing of group discussion activities, may have an impact upon the nature of the pupils' dialogue.