Liquid always has to be heated keeping it in a container. The liquid as well as the container expand when heat is applied. So, the expansion of liquids observed by us is not the real expansion but it is an apparent expansion.
There are two types of expansions of liquids
- Real expansion
- Apparent expansion
Real expansion: If it had been possible to heat a liquid without keeping it in a vessel then the real expansion of the liquid that would be obtained is called real expansion of the liquid. But heating a liquid without a container is not possible. So, considering the expansion of the container the actual expansion of the liquid that is obtained is called the real expansion. It is expressed by Vr.
Apparent expansion: The expansion of liquid apparently observed without considering the expansion of the container is called the apparent expansion of liquid. It is denoted by Va.