Today was 100 minutes of pure whiteboard speed dating. I only changed the groups about every 7 or 8 minutes, but the problems were long and complex enough that we still got through two or three "dates" per problem. All the problems were old AP Physics B ideal gas problems, which worked out really well. These problems really helped students talk about how the internal energy, the work done, and the heat exchanged, the temperature change, and the volume change are interrelated.