The mass of 5 litre of water is 5 kg. Find the density of water in g cm^-3.

Mass = 5 kg
Volume = 5 litre
Density = ?

$\text{Density} = \dfrac{\text{Mass}}{\text{Volume}} \\[1em] \text{Density} = \dfrac{\text{5}}{\text{5}} = 1 \text{kg litre}^{-1}$

Density = 1 kg litre^-1

1 kg = 1000 g; 1 litre = 1000 cm³

1 kg litre^-1 = $\dfrac{\text{1000}}{\text{1000}}$ = 1 g cm^-3

So, density of water = 1 g cm^-3.