Question

Define density
(A) Density of a substance is defined as the weight per unit volume of that substance
(B) Density of a substance is defined as the mass per unit volume of that substance
(C) Density of a substance is defined as the volume per unit mass of that substance
(D) Density of a substance is defined as mass times volume of the substance

Answer 1

Hint : The density of a substance defined how heavy a substance will be for a given size. It is an intrinsic property and also independent of location, such as a change in planet.

Complete step by step answer
Generally, density is the measure of how heavy a substance will be for a particular volume. Properly, it can be defined as the mass per unit volume of that substance. This implies that a particular substance weighs a particular amount for a particular volume of the substance. For example, if a body is said to have a density of say X $kg/m^3$ , this signifies that the substance weighs X kg for 1 $m^3$ of volume of that substance. Water, for example, is said to have a density of about 1000 $kg/m^3$ . Hence, a cubic meter of volume of water will weigh 1000 kg, and 2 cubic meter of volume will thus weigh 2000 kg, and so on.
Density is an intrinsic property, that is, it is independent of the size in which it was used in the measurement. If we increase the size which was used, the mass increases proportionally, hence, density is constant.
From these, we conclude that density is mass per unit volume.
Hence, the correct answer is B.

Note
For clarity, because we say density is said to be intrinsic (or intensive) property does not signify that it is totally independent of other factors which may affect the mass or size. For example, density is affected by temperature, which can make the volume of a substance increase for a particular mass.