Mass per unit volume is best defined as:

Mass per unit volume is best defined as:

• A. Density
• B. Specific gravity
• C. Weight
• D. Mass

Answer: (A)

Density is a measure of how tightly matter is packed into a given space. It is defined as mass per unit volume (ρ = m/V), so it directly expresses how much mass exists in a specific amount of space. This makes density the exact quantity that describes mass per volume: more mass in the same volume means higher density, while the same mass in a larger volume means lower density. Temperature and pressure can influence density because they can change volume, but the fundamental relationship remains mass divided by volume. Mass, by itself, is just the amount of matter and says nothing about how spread out that matter is in space. Weight is the force due to gravity acting on that mass, not a measure of how much mass occupies a given volume. Specific gravity is a ratio comparing a material’s density to the density of water (a dimensionless quantity), which provides a relative sense of density rather than the absolute mass per volume.

Density is a measure of how tightly matter is packed into a given space. It is defined as mass per unit volume (ρ = m/V), so it directly expresses how much mass exists in a specific amount of space. This makes density the exact quantity that describes mass per volume: more mass in the same volume means higher density, while the same mass in a larger volume means lower density. Temperature and pressure can influence density because they can change volume, but the fundamental relationship remains mass divided by volume.

Mass, by itself, is just the amount of matter and says nothing about how spread out that matter is in space. Weight is the force due to gravity acting on that mass, not a measure of how much mass occupies a given volume. Specific gravity is a ratio comparing a material’s density to the density of water (a dimensionless quantity), which provides a relative sense of density rather than the absolute mass per volume.