The density of air is 1.28 g litre^-1. Express it in:

(a) g cm^-3

(b) kg m^-3

(a) The density of air is 1.28 g litre^-1.

1 litre = 1000 cm³

∴ Density of air in g cm^-3 = $\dfrac{\text{1.28}}{\text{1000}}$

Density of air = 0.00128 g cm^-3

(b) Density of air in kg m^-3 = Density of air in g cm ^-3 x 1000 = 0.00128 x 1000 = 1.28 kg m^-3

∴ Density of air in kg m^-3 = 1.28 kg m^-3.