What does specific gravity compare?

Specific gravity is a dimensionless quantity that compares the density of a substance to the density of a reference substance, typically water. This comparison is crucial in various scientific contexts, as it provides insight into how a substance behaves in relation to a common reference point. For instance, the specific gravity of water is defined as 1 g/cm³ at 4°C. When a substance has a specific gravity greater than 1, it is denser than water and will sink, while a specific gravity less than 1 indicates that the substance is less dense than water and will float. Thus, specific gravity is a useful measure in identifying and characterizing substances in both laboratory and practical settings.