What is meant by "thermal expansion" in materials?

Thermal expansion refers to the increase in size of a material when it is subjected to heat. As the temperature rises, the atoms in the material begin to vibrate more vigorously due to the added thermal energy. This increased atomic movement typically results in the atoms moving further apart from one another, causing the overall dimensions of the material—such as length, area, and volume—to increase.

Different materials expand at different rates, a property quantified by their coefficient of thermal expansion. This concept is critical in various applications, including engineering and construction, where understanding how materials behave under temperature changes is essential to avoid issues such as distortion, stress, or failure in structures and components.