An in-depth investigation for middle school and high school readers introduces the various states of matter (solid, liquid, or gas) found in the world around us, describes its constituents, and discusses the various physical factors that influence it, such as the effects of pressure. The effects of heat on solids, liquids, and gases are described, including the processes involved when a substance changes from one state to another and heat transfer through conduction, convection, and radiation, including the properties of good and bad conductors. Includes diagrams, definitions of science words, experiments, glossary, further resources, and index.