What occurs when a material cools, according to thermal expansion principles?

When a material cools, it contracts due to thermal expansion principles. The kinetic energy of the particles within the material decreases as the temperature lowers, causing them to vibrate less vigorously and draw closer together. This results in a decrease in the overall volume of the material, leading to contraction.

Understanding thermal expansion helps to explain why materials behave in this way: when heated, particles gain energy and move further apart, causing expansion, while cooling has the opposite effect. The relationships of temperature, particle motion, and volume changes are fundamental in fields such as engineering and construction, where material properties need to be considered in response to temperature variations.