Abstract
Two types of quantitative chemical experiments using thin metal films such as magnesium, aluminum, and copper were carried out. The atomic weight of Mg or Al was calculated based on the volume of hydrogen gas produced using these metals as thin films reacting with hydrochloric acid. The key point of the experiment was to develop a simple means for weighing the films, which was accomplished by an estimating method; enlarging the shape of a piece of the thin films on the section paper by sixteen times using a copy machine and calculating the weight of the metal by comparing its area or length with the reference. The evolved hydrogen gas was collected into a small test tube in water and the atomic weight of the metal was calculated based on its volume. It should be emphasized that a significant reduction of the metal source was accomplished in this teaching experiment; it requires only 1/30 of the amount of Mg that was used in the conventional method. The second experiment consists of an electrochemical reaction of copper in a copper (II) sulfate aqueous solution in a hand-made small tank ; a sharp triangle thin copper film was used as a cathode and it was demonstrated that the copper was in fact dissolved in the reaction medium through electricity by observing the shape of the copper films.
