If milk is adulterated by the addition of water, what happens to its specific gravity?

When water is added to milk, the specific gravity of the mixture decreases. Specific gravity is a measure of the density of a substance compared to the density of water. Pure milk has a specific gravity that is higher than that of water due to its constituents, which include fats, proteins, and lactose.

When water is introduced into the milk, its overall density decreases because water is less dense than milk. Since specific gravity is calculated as the ratio of the density of the liquid to the density of water at a standard temperature, diluting the milk with water reduces the density of the mixture overall. As a result, the specific gravity of the adulterated milk is lower than that of pure milk, confirming that the correct answer is that it decreases.