Thermal expansion refers to the tendency of matter to change in volume in response to changes in temperature. Different substances expand and contract at different rates when heated or cooled. This is because the atoms and molecules in different materials are arranged differently and have different strengths of intermolecular forces.

Here are some key points about thermal expansion:

* Linear expansion: Expansion in one dimension (length).

* Area expansion: Expansion in two dimensions (surface area).

* Volume expansion: Expansion in three dimensions (volume).

* Coefficient of thermal expansion: A material property that describes how much a material expands or contracts for a given change in temperature.

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