Thermal expansion of solids, liquids and gases — Describe

Give some everyday examples of the applications or consequences of thermal expansion.

Gaps are left in railway tracks and expansion joints in bridges to allow for expansion in hot weather. Bimetallic strips (two metals bonded together, expanding at different rates) are used in thermostats to bend and break/make an electrical contact. Liquid-in-glass thermometers use the expansion of a liquid (e.g. mercury or alcohol) up a narrow tube to indicate temperature. Overhead power cables are hung with slack because they expand and sag more in hot weather.