Give a definition of the density of a substance. In what units is it measured?

The density of a substance ρ (ro) is the mass of a substance m taken in a unit of its volume V and is determined by the formula: ρ = m / V.
Since the mass m has a unit of measurement of kilograms (kg), and the volume V is measured in cubic meters (m ^ 3), the density is measured in kg / m ^ 3.
Density ρ = 1 kg / m ^ 3 means that a substance with a volume of 1 m ^ 3 has a mass of 1 kg.