This case study aimed to determine the nature of student interactions in small groups in an elementary classroom utilizing the Science Writing Heuristic approach. Fifth grade students were audio-recorded over four units of study while working in small groups to generate knowledge claims after conducting student-directed investigations. Analysis consisted of (1) identifying amount of on/off task talk, (2) categorizing on-task talk as generative (talk associated with generating an argument) or representational (talk associated with representing an argument in a final written form), (3) characterizing the generative components of argument, and (4) determining the functions of language used. Results indicate that students were on task 98% of the time. Students engaged in generative talk an average of 25% of the time and representational talk an average of 71% of the time. Students engaged in components of Toulmin's model of argument, but challenging of each other's ideas was not commonplace. Talk was dominated by the informative function (representing one's ideas) of language as it was found 78.3% of the time and to a lesser extent (11.7%) the heuristic function (inquiring through questions). These functions appear to be intimately tied to the task of generating knowledge claims in small groups. The results suggest that both talking and writing are critical to using science discourse as an embedded strategy to learning science. Further, nature and structure of the task are important pedagogical considerations when moving students toward participation in science discourse. (Contains 1 note, 6 tables, and 3 figures.)