What is the specific gravity of pure water as indicated by a hydrometer?

What is the specific gravity of pure water as indicated by a hydrometer?

• A. 1.000
• B. 1000
• C. 0.1000
• D. 10.00

Answer: (B)

Specific gravity compares a liquid’s density to that of water, so for pure water the value is 1.000 when expressed as SG. Hydrometers, however, are often read in density units like kilograms per cubic meter. Pure water at standard conditions has a density of about 1000 kg/m^3, so the instrument would display around 1000. This density corresponds to SG ≈ 1.000 when you relate it back to water. The other numbers don’t reflect water’s density: 0.1000 is far too light, and 10.00 would be far too dense.

Specific gravity compares a liquid’s density to that of water, so for pure water the value is 1.000 when expressed as SG. Hydrometers, however, are often read in density units like kilograms per cubic meter. Pure water at standard conditions has a density of about 1000 kg/m^3, so the instrument would display around 1000. This density corresponds to SG ≈ 1.000 when you relate it back to water. The other numbers don’t reflect water’s density: 0.1000 is far too light, and 10.00 would be far too dense.