What is it called when an object decreases in size or volume due to loss of heat?

When an object decreases in size or volume due to loss of heat, the process is known as contraction. As materials cool, the particles within them typically move slower and are pulled closer together, which results in a decrease in volume. This is a fundamental concept in the study of thermodynamics and material science.

For instance, when metals are heated, they expand; when they cool down, they contract. This principle is essential in various applications, such as ensuring that metal parts fit together properly in construction and manufacturing, as thermal contraction can affect how materials interact.

In contrast, expansion refers to the increase in size or volume of an object as it gains heat. Condensation is the process where gas turns into liquid, often upon cooling, but it does not directly refer to the change in volume of solid objects. Compression involves applying pressure to reduce the volume of a substance, which may not necessarily be related to a loss of heat. Therefore, contraction is the most accurate term for the decrease in size or volume due to cooling.