The object of this study is to develp teaching materials for oxidaiton-reduction and to suggest a unit program for oxidation-reduction reation. Several voltaic cells connected with crystal carphones were made by the immersion of copper wire and six mctal pates (Mg, Al, Zn, Fe, Ni, Cu) into a 0.001 M sulfuric acid solution. When the copper wire and each metal electrode made contact in the solution, a sound with ca. 3100 Hz was generated. Each metal could not be arranged in the order of ionization tendency by :he sound volume. When aluminum plate was amalgamated and other metal plates except magnesium were plated with each salt, these different kinds of meatals could be distinguished and the order ranged from intense to weak sound volume, is consistent with the order of ionization tendency. The metal order obtained from the sound volume is also in agreement with that from the reactivity of each metal in a 0.5 M sulfuric acid solution. The usefulness of the experiment developed in this study was examined in a high scool, about 70% students could put these metals in the order of the ease of oxidation based on the sound volumue using the earphones. A unit program using the experiment to distinguish metals by sound as an introduction to teaching oxdation-reduction reaction is proposed and the relation of oxidation-reduction with other scientifec subiects in school and daily life is also discussed.
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