The specific gravity of water at normal temperature and pressure is 1. Specific gravity is also called relative density. The specific gravity of solids and liquids is the ratio of the density of the substance (completely dense state) to the density of pure H2O (999.972kg/m3) at standard atmospheric pressure and 3.98°C. The specific gravity of a gas refers to the ratio of the density of the gas to the density of air under standard conditions. The specific gravity of a liquid or solid tells whether they sink or float in another fluid.

The relationship between water density and temperature

Water at 4°C has the highest density. When the temperature is higher than 4°C, the density of water becomes smaller and smaller as the temperature increases; when the temperature is lower than 4°C, the density of water becomes smaller and smaller as the temperature decreases. When water solidifies into ice, its volume increases and its density decreases. This characteristic of water is called the abnormal expansion of water.

It starts to increase from 0 degrees, reaches a maximum density at 4 degrees, and then gradually decreases. The functional relationship between the two is as follows: ρ=K/[(t-4)^2]. Where t is the temperature and K is the coefficient.