Density 1

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

Density is mass divided by volume

Mnemonic to help you remember density

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:

Density example

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 standard 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 $=0.036/0.000018=2000\ kg//m^3$