Thermal expansion

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In physics, thermal expansion is the tendency of matter to change in volume in response to a change in temperature. When a substance is heated, its constituent particles move around more quickly and by doing so generally maintain a greater average separation. Materials that contract with an increase in temperature are very uncommon; this effect is limited in size, and only occurs within limited temperature ranges. The degree of expansion divided by the change in temperature is called the material's coefficient of thermal expansion and generally varies with temperature.

Common engineering solids usually have thermal expansion coefficients that do not vary significantly over the range of temperatures where they are designed to be used, so where extremely high accuracy is not required, calculations can be based on a constant, average, value of the coefficient of expansion.

Thermometers are an example of an application of thermal expansion – they contain a liquid which is constrained to flow in only one direction (along the tube) due to changes in volume brought about by changes in temperature.

[change] Other websites

• Glass Thermal Expansion Thermal expansion measurement, definitions, thermal expansion calculation from the glass composition