Question

What is the measurement of how much mass of a substance is contained in a unit volume?

Answer 1

The above question is talking about the density of a substance.
Density of a substance is the ratio of mass per unit volume, whose formula is given as;
$\rho = \dfrac{{mass}}{{volume}}$ ($\rho$ denotes the density of the substance)

Complete step by step answer:
Density is the measurement of how much mass of a substance is contained in a unit volume.
Density is a measure of mass per unit volume. The average density of an object equals its total mass divided by its total volume. As per the formula for density, density of an object is inversely proportional to its volume therefore as the object becomes denser its volume reduces.

Density of an object tells whether an object will sink or float in the water because most of the comparisons are made with respect to water. If the object is dense then it will sink at the bottom of the container in which water is correct. If the object is less dense then it will float at the surface of water.

Note: Specific gravity (also known as relative density, density measured in comparison with water) has no units because it is the ratio of two densities so the numerator and denominator units cancels each other and it is a scalar quantity. By scalar quantity we mean it has only magnitude and no direction .Specific gravity can also be found out by calculating the ratio of weights of the substance and water.