Design-based learning is considered a powerful way to help students apply and develop understanding of science concepts, but research has shown that the success of this approach is not a given. Examining students' understanding of science concepts in various design-based learning contexts has thus continued to be an important field of research. To help advance such work, we explored the affordances of a novel analytic approach for studying data gathered in design-based learning classrooms. We used the "chemical thinking framework," specifically its "conceptual sophistication" dimension, to analyze 10th-grade, chemistry students' design talk and drawings. We gathered this data during small-group design planning and drawing activities in the classrooms of two teachers whose students were designing a product that harnesses chemical energy to change the temperature of a beverage or snack. The findings demonstrate that this analytic approach was able to reveal that students (implicitly) drew on their understanding of several chemistry concepts while designing. Moreover, it showed that students could use everyday as well as more sophisticated understandings regarding a given chemistry concept while designing. This study furthermore unveiled differences in what and how students' design talk and drawings may reveal use of conceptual understanding, and it showed that different student teams may use a unique combination of understandings during design planning and drawing. We describe how this study's analytic approach complements existing approaches in design-based learning research, and how our findings provide implications for research and practice.