This research analyzes students' conceptual change across a semester in an 8th-grade thermodynamics curriculum. Fifty students were interviewed 5 times during their 8th-grade semester and then again preceding their 10th- and 12th-grade years to follow their subsequent progress. The interview questions probed students' understanding of thermodynamics in everyday situations. The analysis of the transcripts first focuses on the full cohort. The analysis then focuses on 2 fairly successful and 2 less successful students in greater detail. Direct quotations provide the primary warrants in the analysis of the 4 case-study students, but the analysis also incorporates 2 new analytical--representational forms to map students' conceptual change trajectories. Ultimately, the results clarify the conceptual change processes through which students' understandings of thermal equilibrium evolve from disjointed sets of context-dependent ideas toward, if not achieving, integrated cohesive perspectives.