My investigation was based on two science tasks on floating and sinking, a topic in which the children had very little prior knowledge. The same four children attended two twenty minute sessions and my aim was to develop their knowledge on why objects float or sink (see Appendices A and B for lesson plans).I planned the tasks after observing the teacher and children in a wide range of subjects (Appendices C and D) to gain an understanding of the teacher's practices and record how the talk was used in the classroom. I particularly observed the types of questions the teacher used, the use of exploratory and presentational talk, how the children were grouped together and the use of dialogic teaching, to see their influence on the children's learning and the teacher's assessment opportunities. Reflecting upon the effectiveness of these methods influenced my own lessons within the class (Appendix E). I used a lot of talk within these lessons, so the post-lesson evaluations (Appendix F) allowed me to observe which talk methods were the most effective, which in turn influenced my science task plans.My TE1 partner observed and took notes of the discussion and activities during these tasks (Appendix G). Worksheets also allowed me to record the children's ideas (Appendices H and I). The first science task was to assess the children's initial understanding of floating and sinking. I documented the general misconceptions that were stated during this session (Appendix J). The second science task, influenced by these misconceptions, provided the children with experiences aimed to develop their understanding.