In the first activity of this unit, students consider how heating and cooling affect molecular motion. The subsequent activities extend this idea to explore the relationship between temperature and the state changes of water. After considering their own experiences with evaporation and condensation, students discover that adding heat to water increases the rate of evaporation and cooling water vapor increases the rate of condensation. Students then investigate what causes moisture to form on the outside of a cold cup. As an extension, students see that at even lower temperatures water vapor can condense on the outside of a container and then freeze to form ice.