Why is it difficult to measure the coefficient of expansion of a liqui

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

Liquids tend to evaporate at all temperatures
Liquids conduct more heat
Liquids expand too much when heated
Their containers also expand when heated
This question was previously asked in
UPSC NDA-1 – 2017
The question asks why it is difficult to measure the coefficient of expansion of a liquid compared to a solid.
When measuring the volume expansion of a liquid, the liquid must be held in a container. When the liquid is heated, the container also gets heated and expands. The observed increase in the volume of the liquid (apparent expansion) is the difference between the actual increase in volume of the liquid (real expansion) and the increase in volume of the container.
$V_{observed} = V_{real, liquid} – V_{expansion, container}$
To find the real coefficient of volume expansion of the liquid, one needs to account for the expansion of the container, which itself has a coefficient of volume expansion (or linear expansion, from which volume expansion can be derived). This adds complexity to the measurement process compared to measuring the expansion of a solid rod or block, where the change in length or volume is directly measured.
Option D correctly identifies this key difficulty: the container’s expansion must be factored in.
Liquids have two coefficients of volume expansion: the coefficient of apparent expansion and the coefficient of real expansion. The coefficient of real expansion of the liquid is equal to the coefficient of apparent expansion of the liquid plus the coefficient of volume expansion of the container material. While liquids generally expand more than solids, the main difficulty in measurement lies in the experimental setup requiring a container that also expands. Evaporation (option A) can also make measurements difficult, especially over long periods or at higher temperatures, but the fundamental challenge inherent to volume expansion measurement of liquids involves the container.