What term describes the mass of a substance occupying a unit volume?

• A. Density
• B. Atomic Mass Number
• C. Compound
• D. Atomic Weight

Answer: (A)

Density is the mass per unit volume. It tells you how much matter is packed into a given space, captured by the formula ρ = m/V, with common units of kg/m^3 or g/cm^3. Temperature affects density because heating generally expands volume, lowering density, while cooling contracts volume, increasing density. Density is an intensive property, meaning it does not depend on how much substance you have. In contrast, atomic mass number is the total count of protons and neutrons in a nucleus, atomic weight is the average atomic mass of an element’s atoms, and a compound is a substance made from two or more elements chemically bonded. So the term describing mass per unit volume is density.