Which term defines the ratio of a material’s weight to the weight of an equal volume of water?

Which term defines the ratio of a material’s weight to the weight of an equal volume of water?

• A. Grain lines
• B. Habit
• C. Twinned crystal
• D. Specific gravity

Answer: (D)

Specific gravity is the comparison of how heavy a material is to how heavy an equal volume of water is. It’s a dimensionless ratio, so it describes density relative to water without regard to the sample’s size or shape. Since water’s density is about 1 g/cm³ (at standard conditions), the specific gravity value essentially reflects the material’s density in those units, making it a convenient way to compare densities quickly. In practice, you can determine it by weighing the sample in air and then weighing it while submerged in water—the loss of weight due to buoyancy corresponds to the displaced water, giving the ratio of the two weights. The other terms describe crystal form or surface features, not how dense a material is compared with water.

Specific gravity is the comparison of how heavy a material is to how heavy an equal volume of water is. It’s a dimensionless ratio, so it describes density relative to water without regard to the sample’s size or shape. Since water’s density is about 1 g/cm³ (at standard conditions), the specific gravity value essentially reflects the material’s density in those units, making it a convenient way to compare densities quickly. In practice, you can determine it by weighing the sample in air and then weighing it while submerged in water—the loss of weight due to buoyancy corresponds to the displaced water, giving the ratio of the two weights. The other terms describe crystal form or surface features, not how dense a material is compared with water.