In this unit students are asked to mix materials together and look closely at what happens. From this experience, plus teacher input, they are introduced to the concept that matter is made of small particles which cannot be seen, but can be manipulated. Students learn the difference between a physical and a chemical change and that there are four ways to tell when a chemical reaction has taken place: the formation of a gas; a change of color; formation of a solid; and the production of heat or light--fast or slow oxidation. This document contains the lists of materials needed to do the activities, a discussion of the use of process skills, a list of the unit objectives by lesson, vocabulary, teacher background information, ten lessons, three quizzes, a unit test, and supplementary information to teach chemistry to fourth graders. Each lesson also includes procedures and a reproducible worksheet. (CW)