Thermal expansion is the expansion of a material when its temperature rises. Generally, solids expand the least, followed by liquids and then gases.
Uses of expansion
Rivets are used to join materials . A red-hot rivet is passed through holes in two metal plates and then hammered until the ends are rounded . As the rivet cools, it contracts and pulls the two plates tightly together .
A cap or lid may stick to a bottle. Heating the lid causes it to expand, so the lid loosens and can be removed.
A steel tyre may be fitted to a locomotive while the tyre is very hot. It then cools and contracts so that it fits tightly on the wheel.
Consequences of Expansion
Metal bridges and railway lines expand on hot days and there is a possibility that they might buckle. To avoid this, bridges are made in sections, with expansion joints between the sections.
Glass containers may crack when hot liquid is placed in them This is because the inner surface of the glass expands rapidly , before the heat has conducted through to the outer surface.