expansion, in physics, increase in volume resulting from an increase in temperature. Contraction is the reverse process. When heat is applied to a body, the rate of vibration and the distances between the molecules composing it are increased and, hence, the space occupied by the body, i.e., its volume, increases. This increase in volume is not constant for all substances for any given rise in temperature, but is a specific property of each kind of matter. For example, zinc and lead undergo greater expansion in a one-degree rise in temperature than do silver or brass. Since solids have a definite shape, each linear dimension of the solid increases by a proportional amount for a given temperature increase. The amount that a unit length along any direction of a substance increases for a temperature increase of one degree is called the coefficient of linear expansion of the substance. Most liquids also expand when heated. However, since liquids do not have a definite shape, it is the expansion of their volume as a whole that is relevant rather than the increase in a linear dimension. The amount of expansion that a unit volume (e.g., a cubic centimeter or a cubic foot) of any substance undergoes per one-degree rise in temperature is called its volume coefficient or coefficient of cubical expansion and is listed as a property of that substance. The coefficient of linear expansion can be calculated by dividing the coefficient of cubical expansion of the substance by three. When the amount of expansion of a given length of a substance has been determined experimentally, the linear coefficient is calculated by dividing the total amount of expansion by the product of the original number of length units and the number of degrees of rise in temperature. Gases also exhibit thermal expansion. The coefficient of expansion is about the same for all the common gases at ordinary temperatures; it is 1/273 of the volume at 0°C; per degree rise in temperature. The Kelvin, or absolute, scale is based upon this behavior (see Kelvin temperature scale). Charles's law concerning the expansion of gases states that the volume of a gas is directly proportional to its absolute temperature (see gas laws). Liquids differ from each other as do solids in their expansion coefficients. Water, unlike most substances, contracts rather than expands as its temperature is increased from 0°C; to 4°C;; above 4°C; it exhibits normal behavior, expanding as the temperature increases.

Increase in volume of a material as its temperature is increased, usually expressed as a fractional change in dimensions per unit temperature change. When the material is a solid, thermal expansion is usually described in terms of change in length, height, or thickness. If a crystalline solid has the same structural configuration throughout, the expansion will be uniform in all dimensions. Otherwise, there may be different expansion coefficients and the solid will change shape as the temperature increases. If the material is a fluid, it is more useful to describe the expansion in terms of a change in volume. Because the bonding forces among atoms and molecules vary from material to material, expansion coefficients are characteristic of elements and compounds.

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Expansion may refer to:

  • In physics:

*expansion of space,
*thermal expansion,
*expansion fan.

  • In computer hardware: an expansion card
  • In computer programming: JEE5 developing tool in-line expansion
  • In engineering expansion is the increase in the size of a material and or other products such as the expansion of plastic or metal. By Matthew Barber
  • In computer gaming:

*an expansion pack
*(in real time strategy games like Starcraft) building a secondary base to gather more resources.

  • In mathematics:

*polynomial expansion
*Taylor Expansion
*expansion of a graph
*the converse of a reduct, in model theory or universal algebra.

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