What is the measure of the amount of matter in an object per unit volume?

• A. Mass per volume
• B. Weight
• C. Volume
• D. Density

Answer: (D)

Density is the measure of the amount of matter in a given volume. It tells you how tightly packed the material is. It’s calculated as mass divided by volume, so more mass in the same volume means higher density, while the same mass spread over a larger volume means lower density. This explains why a metal block feels heavier than a wooden block of the same size, and it also underpins buoyancy—objects with greater density than the surrounding liquid tend to sink, while less dense ones float. The standard units are kg/m^3 (or g/cm^3), and while “mass per volume” describes the same idea, the conventional term for the measure is density.