This volume is the twenty-sixth in a series of 29 coordinated MINNEMAST units in mathematics and science for kindergarten and the primary grades. Intended for use by third-grade teachers, this unit guide provides a summary and overview of the unit, a list of materials needed, and descriptions of eight groups of lessons. The purposes and procedures for each activity are discussed. Examples of questions and discussion topics are given, and in several cases ditto masters, stories for reading aloud, and other instructional materials are included in the book. In this unit, chemical and physical properties of materials are examined. Properties studied are hardness, weight, volume, density, color separation, shape, solubility, and chemical reaction. (SD)