What does specific gravity measure?

Specific gravity measures the density of a substance relative to the density of water. It is a dimensionless quantity that provides insight into how heavy a substance is compared to water at a specific temperature, typically 4 degrees Celsius (where water is densest).

When you calculate specific gravity, you take the density of the substance and divide it by the density of water. A specific gravity less than 1 indicates that the substance is lighter than water and will float, whereas a specific gravity greater than 1 suggests that the substance is denser than water and will sink.

This measurement is important in various fields, including wastewater treatment, because it helps in identifying substances, understanding their behavior in water, and determining their concentration or purity. Other options involve different concepts like volume comparison, temperature measurement, or dissolved solids, which do not accurately describe what specific gravity is intended to measure.