Entropy and a Rubber Band A familiar demonstration of entropy changes in spontaneous processes is the temperature change observed when a lubber band is held against the cheek, stretched, and then released. We have found that a simple and perhaps more effective demonstration involving entropy and rubber is the warming of a stretched rubber bmd. The band is attached to a large weight (500 g), suspended from a rigid clamp, and warmed by means of an electric heat gun or a. portable hair dryer. (A direct flame should be avoided, of course, because of the resultine deterioration of the rubber.) Percentible contraction occurs auicklv. Thoueh the students' ) in thG endothermic but snonreaction is initiallv oneof amazement. thev soon r&e (w&h a little ~ r o d d i n n that
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