When looking at density, it is important to first understand the states of matter. The three common states of matter are solidsliquids and gases.

Understanding Density

The density of an object is its mass for a given volume. For example, let’s compare two blocks with the same volume.

  • The high-density block has a lot of mass packed into its volume
  • The low-density block has a lower mass packed into the same volume

Calculating Density

To calculate the density of an object, we need:

  • The mass of the object
  • The volume of the object

The mass of the object can be measured using a balance and a measuring cylinder can be used to measure the volume of a liquid. To measure the volume of a solid, measure its side.

The equation to calculate density is:

  • ρ = Density in grams per centimetre cubed (g/cm3)
  • M = Mass in grams (g)
  • V = Volume in centimetres cubed (cm3)


A rock has a mass of 15 kg and a volume of 1 m3. Calculate the density.

Looking back at the equation:

Density (g/cm3) = Mass (g) ÷ Volume (cm3)

We know 15 kg = 15000 g and 1 m3 = 100 cm3

So. density = 15000 g ÷ 100 cm3 = 150 g/cm3