A hydrometer is used to measure which property?

A hydrometer is used to measure which property?

• A. The density of water
• B. The volume of a container
• C. The pressure of a gas
• D. The temperature of air

Answer: (A)

A hydrometer works on buoyancy: the float sinks farther in less-dense liquids and sits higher in denser ones. The position it settles on is directly tied to how dense the liquid is, and these instruments are calibrated in terms of density (often expressed as specific gravity relative to water). Since water has a well-defined density and serves as the reference point, the reading effectively tells you the liquid’s density, i.e., how dense the liquid is compared with water. This is why a hydrometer is used to determine density rather than volume, pressure, or temperature.

A hydrometer works on buoyancy: the float sinks farther in less-dense liquids and sits higher in denser ones. The position it settles on is directly tied to how dense the liquid is, and these instruments are calibrated in terms of density (often expressed as specific gravity relative to water). Since water has a well-defined density and serves as the reference point, the reading effectively tells you the liquid’s density, i.e., how dense the liquid is compared with water. This is why a hydrometer is used to determine density rather than volume, pressure, or temperature.