What is specific gravity?

What is specific gravity?

• A. The density of a substance relative to air.
• B. The ratio of density to the density of water (water = 1).
• C. The vapor density relative to air.
• D. The solubility relative to water.

Answer: (B)

Specific gravity is the ratio of a substance’s density to the density of water, with water defined as 1. This makes the value unitless. It tells you how heavy or light a substance is compared with an equal volume of water. If the SG is greater than 1, the substance is denser than water and will tend to sink; if the SG is less than 1, it’s lighter than water and may float. This differs from vapor density (which compares a vapor’s density to air) and from solubility (which measures how well something dissolves in water). For example, a liquid with density 1.2 g/cm3 has an SG of 1.2, while one with 0.8 g/cm3 has an SG of 0.8.

Specific gravity is the ratio of a substance’s density to the density of water, with water defined as 1. This makes the value unitless. It tells you how heavy or light a substance is compared with an equal volume of water. If the SG is greater than 1, the substance is denser than water and will tend to sink; if the SG is less than 1, it’s lighter than water and may float. This differs from vapor density (which compares a vapor’s density to air) and from solubility (which measures how well something dissolves in water). For example, a liquid with density 1.2 g/cm3 has an SG of 1.2, while one with 0.8 g/cm3 has an SG of 0.8.