Thermal expansion is the tendency of matter to increase in length, area, or volume, changing its size and density, in response to an increase in temperature (usually excluding phase transitions).In simple words, the change in size of a body due to heating is called thermal expansion. Substances usually contract with decreasing temperature (thermal contraction), with rare exceptions within limited temperature ranges (negative thermal expansion). The SI unit of thermal expansion is inverse Kelvin (1/K).
Temperature is a monotonic function of the average molecular kinetic energy of a substance. In simple words, temperature is the measure of kinetic energy of a body or the measure of hotness or coldness of a body. As energy in particles increases, they start moving faster and faster, weakening the intermolecular forces between them and therefore expanding the substance.When a substance is heated, molecules begin to vibrate and move more, usually creating more distance between themselves.
