Solution:

The mass of 5 liters of water is 5 kg.

Since              1 litre  =  $10^{-3} m^{3}$
         5 litre  = $5 \times 10^{-3} m^{3}$
Density = $\frac{(Mass of a substance)}{(volume of the substance)}$  OR   D= $\frac{m}{v}$
Density = $\frac{(5 kg)}{(5 \times 10^{-3}} m^{3})$
= 1000 kg $m^{-3}$ 

The density of water is 1000 kg $m^{-3}$