Density is defined as what, in terms of mass and volume?

• A. The amount per unit size
• B. The amount per unit area
• C. The gravitational force
• D. The resistance to flow

Answer: (A)

Density measures how much mass is packed into a given amount of space. The correct idea is mass per unit volume, expressed as density = mass / volume. This means two objects made of the same material share the same density, even if their sizes differ—the larger object simply contains more mass in the same amount of space. Common units are kilograms per cubic meter or grams per cubic centimeter.

This concept differs from other ideas: gravitational force is weight (mass under gravity), resistance to flow is viscosity, and mass per area would be areal density. Therefore, describing density as mass per unit volume is the precise definition.