Final answer:
Thermal expansion is the increase, or decrease, in the size of a body due to a change in temperature. An increase in temperature causes an increase in the kinetic energy of atoms, leading to an increase in volume. Examples of thermal expansion include the expansion of alcohol in a thermometer and the use of expansion joints in railroad tracks and bridges.
Step-by-step explanation:
Thermal expansion is the increase, or decrease, of the size (length, area, or volume) of a body due to a change in temperature. This occurs because an increase in temperature causes an increase in the kinetic energy of the individual atoms, resulting in an increase in the volume of the material. Gases are especially affected by thermal expansion, while liquids and solids also undergo thermal expansion to a lesser extent.
An example of thermal expansion can be seen in the expansion of alcohol in a thermometer. In addition, railroad tracks and bridges have expansion joints to allow them to freely expand and contract with temperature changes.