Scientific sense-making is a process in which theory and evidence are brought into coordination. This work examines the conditions for the development of scientific sense-making in fifth and sixth grade classroom science lessons. Classroom activities that were structured as a series of presentations are compared with activities structured more as conversations with respect to their consistency with, and support of sense-making. Features of conversation such as displaying the relevance of one turn to the previous turn are shown to support the movement of ideas during the activity and to display important elements of sense-making. A close relation between conversation and sense-making is proposed. (Author/ZWH)