Piezoelectricity is an electrical effect that occurs when mechanical stress is applied to certain materials, e.g., quartz crystals, Rochelle salts, and barium titanate. The sound of a wrist watch alarm or a smoke detector is made by a piezoelectric transducer. Piezoelectric crystals are used in cigarette and gas stove lighters, where tension produced by a lever produces enough voltage to create a spark. The activity here involves making a simple apparatus to demonstrate piezoelectricity.