What does thermal expansion refer to?

Thermal expansion refers specifically to the tendency of matter to change its volume in response to temperature changes. As a substance is heated, its particles move more vigorously and tend to occupy more space, leading to an increase in volume. Conversely, when a substance is cooled, its particles slow down and may occupy less space, leading to a decrease in volume. This principle applies to solids, liquids, and gases and is a fundamental concept in thermodynamics.

Understanding thermal expansion is crucial in various applications, including engineering, construction, and mechanical systems, as it can impact material integrity, structural stability, and performance. For example, metals expand when heated and contract when cooled, which must be accounted for in the design of structures such as bridges and railways to prevent damage or failure.