True or false: the coefficient of thermal expansion governs the way a substance expands or contracts when it is heated or cooled

It is true because Thermal expansion is the tendency of matter to change in shape, area, and volume in response to a change in temperature, through heat transfer. Temperature is a monotonic function of the average molecular kinetic energy of a substance. When a substance is heated, the kinetic energy of its molecules increases. Thus, the molecules begin moving more and usually maintain a greater average separation.