Question

explain the working of the hydrometer

Answer 1

A hydrometer or areometer is an instrument used for measuring the relative density of liquids based on the concept of buoyancy. They are typically calibrated and graduated with one or more scales such as specific gravity

Answer 2

The point at which the surface of the liquid touches the stem of thehydrometer correlates to specific gravity. ... The hydrometer makes use of Archimedes' principle: a solid suspended in a fluid is buoyed by a force equal to the weight of the fluid displaced by the submerged part of the suspended solid.