Gases, Liquefaction of (Encyclopedia of Science)
Liquefaction of gases is the process by which a gas is converted to a liquid. For example, oxygen normally occurs as a gas. However, by applying sufficient amounts of pressure and by reducing the temperature by a sufficient amount, oxygen can be converted to a liquid.
Liquefaction is an important process commercially because substances in the liquid state take up much less room than they do in their gaseous state. As an example, oxygen is often used in space vehicles to burn the fuel on which they operate. If the oxygen had to be carried in its gaseous form, a space vehicle would have to be thousands of times larger than anything that could possibly fly. In its liquid state, however, the oxygen can easily fit into a space vehicle's structure.
Liquefaction of a gas occurs when its molecules are pushed closer together. The molecules of any gas are relatively far apart from each other, while the molecules of a liquid are relatively close together. Gas molecules can be squeezed together by one of two methods: by increasing the pressure on the gas or by lowering the temperature of the gas.
Critical temperature and pressure
Two key properties of gases are important in developing methods for their liquefaction: critical temperature and critical pressure. The critical temperature of a gas is the temperature at or above which no...
(The entire section is 1441 words.)
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