This analysis focuses on two writing activities required by a middle school science curriculum unit to demonstrate how particular forms of writing guide students to frame their knowledge in important ways. Following the completion of charts and "Think and Write" questions related to a single scientific phenomenon, I trace how students identify the phenomenon first as a "little red," then call it "rust," and later adopt the scientific term "iron oxide" and formula, "Fe[subscript 2]O[subscript 3]," in writing. While these written forms appear to be objective, this analysis takes a situated approach to interaction and shows how students are socialized to these more sophisticated written forms through practices such as selecting, organizing, renaming, and repackaging experiences from laboratory activities and discussion. This interactive perspective illustrates the very social nature of writing, as well as the importance of social interaction in helping students come to identify and appropriate valued forms of scientific language. (Contains 10 figures.)