In the action-research phase of the Learning in Science Project, four groups of people worked on problems identified in the project's second (in-depth) phase. The Chemistry Action-Research Group considered problems related to the teaching and learning of ideas associated with particles and physical/chemical changes. Based on findings during the in-depth phase, three units were developed, each unit containing: (1) information on children's and scientists' ideas related to phenomena considered in the unit; (2) a survey to help teachers clarify their own views and to establish views of students in their classrooms; and suggested teaching activities designed to modify children's views to help them make more sense of their world. The first unit ("Burning") focuses on the burning of a candle. The second unit ("Reactions") examines a range of phenomena, each of which involves a chemical reaction. The third unit ("Heating and Cooling") considers what happens when things are heated and introduces a simple particle model to explain what is happening. Each of the units was then field tested. Results of the testing for the "Burning" and "Heating and Cooling" units are presented and discussed, focusing on the extent to which children's views changed before and after the unit. (JN)