Releasing Energy through Reactions in Batteries

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Releasing Energy through Reactions in Batteries Reactions that involve a change in oxidation number are called oxidation-reduction reactions. An element is oxidized if the oxidation number has become more positive in value. The term reduction describes the opposite process, in which the oxidation number becomes more negative in value. In the same equation, for example, the hydrogen is reduced. The oxidation number has changed from +1 to 0. If everything is counted through the entire equation, oxidation and reduction are equal and balance to 0. When electric energy is needed, batteries and fuel cells are one way to provide it. A battery chemically stores and then releases energy. A fuel cell converts energy produced by a chemical reaction directly into usable power. Batteries range in size from single-cell models smaller than coins to multi-cell units that fill large rooms. Portable radios, pocket calculators, watches, and hearing aids are typical devices powered by batteries. Very large battery installations supply standby energy for equipment such as that in telephone exchanges. Alessandro Volta, an Italian professor, devised the first battery in 1800 to provide steady electric current for study and practical use. Before that time, only static electricity--a novelty with no practical value--could be produced. Batteries are either primary or secondary. A primary battery produces its energy by consuming one of the chemicals it contains. When the chemical is gone, the battery no longer produces energy and must be replaced. The carbon-zinc batteries used in flashlights and tape recorders are primary. Secondary batteries, or storage batteries, obtain energy by transforming certain kinds of chemicals ... ... middle of paper ... ...mation of a green patina, or film, called verdigris, which is composed of copper carbonate. In many instances buildings with copper-clad roofs and trim are deliberately allowed to develop patinas because the color is considered attractive. Corrosion takes place at a much faster rate in heavily industrialized areas that have high levels of sulfur and nitrogen pollutants in the atmosphere. These compounds combine with moisture in the air to produce extremely corrosive acids. Metals may be protected from corrosion by coating them. A variety of coating processes are used, including painting, electroplating with chromium, or plating with zinc, which is called galvanizing. Alloying steel with chromium or chromium and nickel produces stainless steel, which is resistant to rusting. Plastics, ceramics, and certain rubber compounds are also used to coat metals.

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