# Density

Density is a measure of how tightly packed the molecules of a solid, liquid or gas are. The formula for calculating density is:

The dense city (density) was so dense they built motorways over any vegetation.

NOTE:

`m =` mass in kilograms (`kg`)

`V =` volume in cubic metres (`m`)

`D =` Density in kilograms per metre cubed (`kg//m^3`)

**Example 1**

John wants to measure the density of a rock. He finds the volume with the apparatus shown below:

The mass of the rock was measured as being 36g. What is the density of the rock?

**Answer:**

`Density=(mass)/(volume)`

First convert everything to SI units

Mass of the rock `= 36g = 0.036\ kg`

Volume of rock `=36cm^3-18cm^3=18cm^3=0.000018m^3`

Density of the rock `=0.036/0.000018=2000\ kg//m^3`