How is the weight of water defined in measurements of specific gravity?

In measurements of specific gravity, the weight of water is defined as 1. Specific gravity is a dimensionless quantity that compares the density of a substance to the density of a reference substance, which in most cases is water. By convention, the specific gravity of water at 4 degrees Celsius, where it is densest, is assigned the value of 1.

This standard allows for easier comparison when evaluating the specific gravity of other substances. If a substance has a specific gravity greater than 1, it is denser than water and will sink. Conversely, if it has a specific gravity less than 1, it is less dense than water and will float. This reference point is crucial in HAZMAT operations, as it helps responders quickly assess the behavior of hazardous materials when mixed with water or when identifying potential risks related to spills or leaks.