What does the term 'thermal expansion' refer to?

The term 'thermal expansion' refers to the tendency of matter to change in volume in response to changes in temperature. When a material is heated, its particles tend to move faster and spread apart, leading to an increase in volume. This principle is fundamental in various engineering applications, including construction, as it can significantly impact the integrity and performance of structures. Understanding thermal expansion is essential for ironworkers since they need to account for the effects of temperature changes on metals and other materials used in construction.

The other options provided do not accurately describe thermal expansion. The increase in weight of a material when heated is not a recognized property related to thermal expansion; the weight remains constant regardless of temperature. Additionally, while materials do shrink upon cooling (which is related to thermal contraction), this is not the definition of thermal expansion. The process of changing states from liquid to solid due to temperature change describes a phase change and is separate from expansion or contraction concepts.