Specific Gravity is a dimensionless ratio comparing to water density at 4°C. Which option correctly describes this?

Specific Gravity is a dimensionless ratio comparing to water density at 4°C. Which option correctly describes this?

• A. It is a measure of thermal conductivity.
• B. It is a ratio of mass to volume for the material.
• C. It is a dimensionless ratio of the material's density to water density at 4°C.
• D. It is always greater than 1.

Answer: (C)

Specific gravity is the dimensionless ratio of a material’s density to the density of water at 4°C. Because both densities use the same units, the units cancel and you get a pure number. Water at 4°C has its maximum density (about 1.0 g/cm³), so the specific gravity shows how many times denser or lighter the material is compared with water. It’s not a measure of thermal conductivity, and it’s not simply the mass per volume of the material itself—that latter quantity is density, while specific gravity is that density divided by water’s density. And it isn’t always greater than 1; materials can be less dense than water, giving a specific gravity below 1.

Specific gravity is the dimensionless ratio of a material’s density to the density of water at 4°C. Because both densities use the same units, the units cancel and you get a pure number. Water at 4°C has its maximum density (about 1.0 g/cm³), so the specific gravity shows how many times denser or lighter the material is compared with water. It’s not a measure of thermal conductivity, and it’s not simply the mass per volume of the material itself—that latter quantity is density, while specific gravity is that density divided by water’s density. And it isn’t always greater than 1; materials can be less dense than water, giving a specific gravity below 1.