Modeling Approach to Chemistry: From Observable Changes to Particle Model of Matter
Dr. Donghong Sun, of Montgomery High School in Skillman, NJ, led a terrific 3 hour workshop on Sunday, Nov 18 at Teachers College. The workshop topic was “An Approach to Modeling in Chemistry: from observations and experiments to particle models of matter.” There were more signups than could fit in room 404 (our usual venue), so the workshop took place in 414, a somewhat larger room. Dr. Sun, a chemistry PhD at Columbia and a member of the PhysicsTeachersNYC Board, had prepared a detailed, 27-page set of materials, including real data from her students’ experiments. She led us through the analysis, interpretation, whiteboarding, and discussion of six experiments directed toward determining whether or not the mass changed in the following processes: separating the strands of a pad of steel wool, ice melting, sugar dissolving, two transparent solutions being mixed and forming a milky, non-transparent liquid, Alka-Seltzer producing bubbles in water, and steel wool burning in air. She asked us to determine if the mass changed in each case and to explain and illustrate what happened as best we could by using diagrams showing how the particles of the substances might “look” before and after.
Dr. Sun “modeled” good discourse management skills in guiding the discussion, insisting that we pay close attention to the evidence, and gently but firmly discouraging us from using ah-hoc explanations based on authority. As a result, the discussions were extraordinarily lively, stimulating many creative ideas, and bringing out a wide range of interesting and worthwhile scientific and pedagogical issues. The experiments and the students’ evidence proved to be very productive, fueling evidence-based interpretations in terms of particle models, chemical vs. physical changes, and the importance of closed vs. open systems in actually determining whether or not mass is conserved. We all were stimulated to exercise our brains in both “student mode” and “teacher mode,” and we gained concrete experience with the actual practice of modeling instruction, as well as with some very specific, usable experiments and classroom lessons. After the workshop, we repaired to our usual haunt, the Sezz Medi Neapolitan Café, for our customary jolly lunch.