The coefficient of linear thermal expansion for aluminum is 24 x 10^-6 in the International System of Units. This value represents the extent to which aluminum expands or contracts in one direction in response to temperature changes.
Thermal expansion occurs when the average distance between molecules in a material increases due to an increase in temperature. Materials also contract when the temperature drops, but this isn't as significant or common as thermal expansion. The coefficient of thermal expansion of materials is important in material science and construction, because of the damage caused on especially hot days to structures such as bridges and towers.