The concept of a chemical reaction (as opposed to physical mixing, dissolution, or change of state) is developed in this five-part unit. In addition, the ideas that chemical reactions involve the formation of new substances and that mass is conserved in a chemical reaction are stressed. Part 1 discusses unit objectives and considers teachers' views on chemical reactions. Part 2 is an 11-item instrument designed for teachers to examine their views and to determine student views before and after instruction. Part 3 discusses scientists' views of chemical reactions (and dissolving) and lists correct answers to the survey instrument presented in part 2. Scientists' views are contrasted with children's views of four common events, using comments obtained from the in-depth phase of the Learning in Science Project. Events considered include: vitamin C tablet reacting in water; precipitation; rusting nails; and dissolving. Part 5 lists a series of activities designed to build on children's views where these views are essentially similar to those of scientists, and to challenge and change children's views where these are found to be inconsistent or incompatible with those of scientists. An overall framework to the sequence of activities (in flowchart format) is included. (JN)