Chemistry Regents Practice Test 2025 – The All-in-One Guide to Exam Success!

A hydrometer operates based on the principle of buoyancy, which is illustrated by Archimedes' principle. When a hydrometer is placed in a liquid, it displaces a volume of that liquid equal to the weight of the hydrometer. The level to which the hydrometer sinks into the liquid is indicative of the liquid's density; liquids with higher densities will cause the hydrometer to float higher, while lower-density liquids will allow it to sink further.

This buoyant force allows the hydrometer to provide a measurement that can be correlated to the density of the liquid. This is crucial for applications such as determining the specific gravity of liquids, which can be essential in many laboratory and industrial settings.

The other options involve concepts that do not directly pertain to the operation of a hydrometer. The amount of heat does not influence buoyancy directly; electrical conductivity relates to the liquid's ionic composition but is not relevant for measuring density; and while the presence of solutes can affect the overall density of a solution, the hydrometer itself functions purely through buoyancy rather than measuring the solutes directly.