Thermal Expansion

Thermal expansion is the expansion in matter with increased temperature; it occurs in all three phases of matter.

If an object is heated, the kinetic energy of the molecules increases, resulting in a greater average distance between the molecules. Consequently, the object expands.

There are three categories of thermal expansion: Linear, areal, and volume.

Solids undergo all three types of expansion, while liquids and gases exhibit only volume expansion.

Linear expansion is the change in length of a substance by applying temperature, proportional to the initial length and change in temperature. The proportionality constant is the coefficient of linear expansion.

Similarly, areal expansion is the change in area of a body when heated. The proportionality constant is the coefficient of areal expansion.

Further, volume expansion is the change in volume of a body when heat is applied. Here, the proportionality constant is the coefficient of volume expansion.

An exception to this is water; water expands when decreasing the temperature between 4 and 0 degrees Celsius, as its density is highest at 4 degrees Celsius.