Why is it difficult to measure the coefficient of expansion of a liquid than solid ?

Measuring the thermal expansion of a liquid is inherently more complex than measuring that of a solid because liquids do not have a fixed shape and must be held in a container [1]. When the system is heated, both the liquid and the containing vessel undergo thermal expansion simultaneously. Consequently, the observed change in the liquid level represents only the 'apparent expansion,' which is the difference between the real expansion of the liquid and the volume expansion of the container. To determine the 'real' coefficient of expansion, one must mathematically account for the expansion of the vessel, a factor that is not present when measuring the linear or volume expansion of a self-supporting solid. While liquids do evaporate, the primary experimental difficulty in expansion measurement specifically arises from the concurrent expansion of the apparatus.

Sources

1. [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 7: Particulate Nature of Matter > 7.2.2 Liquid state > p. 104