Nearly all elements react with oxygen in a process referred to as oxidation. This process involves the addition of oxygen to a substance. A related process, reduction, involves the removal of oxygen. Oxidation is important because this reaction occurs in the body's metabolism as well as in various industrial processes. It is a well known, if little understood, process seen in combustion and the appearance of rust on materials made from iron.
When sufficient heat and oxygen are applied to fuels made from the right elements, such as carbon and/or hydrogen, combustion occurs. The fuel is oxidized and energy, in the form of heat, is released. Combustion is the basis for much of the modern world's energy usage.
Photosynthesis is another important process involving oxidation. Plants take in carbon dioxide and water and, with the energy gained from sunlight, create glucose sugar and pure oxygen. The glucose serves as food for the plant and the pure oxygen is expelled into the environment.
Oxidation also occurs within the bodies of animals. In catabolic reactions, which are essentially the opposite of photosynthesis, glucose and oxygen react to form carbon dioxide and water. Though this is the reverse of photosynthesis, it is oxidation because the carbon in the glucose gains oxygen when it becomes carbon dioxide.
Dry Cell Batteries
The zinc cylinder in a common dry cell battery is oxidized as the manganese dioxide paste inside it is reduced. This reaction produces the battery's voltage. Other types of batteries, such as mercury or nickel-cadmium batteries, also depend on oxidation to produce voltage.
Oxidation is also the reaction responsible for the creation of metal corrosion or rust. When the water in moist air makes contact with a metal surface, some of the metal molecules add oxygen and lose strength. In the case of iron or steel, the surface of the metal changes color, often becoming reddish, and pieces of this oxidized surface flake off, weakening the structure.
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