Introduction – Expansion in Liquids

When liquids are heated, their temperature increases, leading to the expansion of the liquid volume, and the containing vessel equally expands at the same time.

Hence, real expansion is the addition of apparent expansivity and expansion of the containing vessel.

Real expansion of the liquid = Apparent expansion + expansion of the container

The real cubic expansivity of a liquid can be derived from the relationship above.

The real or absolute cubic expansivity (γ_r) of a liquid is the increase in volume per unit volume per degree rise in temperature.

The difference in expansion between the containing vessel and the volume of the liquid is called the apparent expansion of the liquid (γ_a)

Therefore, the apparent cubic expansivity (γ_a) of a liquid is the increase in volume per unit volume per degree rise in temperature when the liquid is heated in an expansible container.

The real expansivity of a liquid (γ_r) is always more than the apparent expansivity (γ_a), because the apparent expansivity also depends on the cubic expansivity of the material.

The difference between the real and apparent expansivity of a liquid is the cubic expansivity of the vessel.

\( \scriptsize \gamma_r = \gamma_a \: + \: \gamma \)