Changes, Changes: Changing States by Will Hurd

The fourth state of matter?

Will Hurd's Changing States: Solids, Liquids, and Gases (Do It Yourself) (Heinemann, 2009) takes the reader through an engaging and unusually cogent discussion of the usual three states of matter--solid, liquid, gas--which begins with marbles in a jar and amplifies the discussion with experiments demonstrating the effects of heat and agitation upon the atoms and molecules which make up matter and which cause readily observable changes in their states.

Hurd spends a good part of his text on the basics of physical change, the necessary jumping-off point for the study of elementary science and common sense activities in daily life. Particularly apropos is his example of the similarities and differences between two familiar objects:

For example, a golf ball and a ping-pong ball are about the same size. They take up about the same amount of space, so they have about the same volume. Even though the golf ball and the ping-pong ball have about the same volume, the golf ball is heavier. There is more matter in a golf ball. A golf ball's mass is greater than that of a ping-pong ball.

Concentrating upon the particular behavior of water, the author has designed activities in which the familiar processes of freezing, boiling, melting, and even sublimation, (in which ice cubes in a freezer go from solid to gas without passing through the liquid state) produce changes in physical state. Held also covers the water cycle as an everyday experience which illustrates these changing states of water.

Chemical change is a bit harder to present to elementary students, and Held offers an activity in which the mixing of vinegar and baking soda inflates a balloon with the carbon dioxide gas produced by the chemical change produced by the interaction. Another example includes oxidation in the process of rust and of burning.

And that intriguing fourth state of matter? Held points to the flame produced by combustion as an illustration of that tricky state--"the fourth state of matter called plasma, defined as "a gas that has an electrical charge" as found in flame, lightning, the sun--and the familiar plasma television set. In closing Held even introduces readers to the even greater mystery in the science of physical states--the posited existence of so-called "dark matter" throughout the universe.

Detailed instructions and illustrations for correlated activities, clear explanations, and ample color photographs make this title an interesting. engaging, and hands-on explanation of this subject for elementary science students to expand classroom activities and inspire science projects. Some other related titles in Heinemann Library's excellent Do It Yourself series include Experiments with Light (Do It Yourself), Magnets: Magnetism (Do It Yourself), Gravity (Do It Yourself), and Experiments With Sound: Explaining Sound (Do It Yourself).