Question

The quantity called mass density is the mass per unit volume of a substance. Express the following mass densities in SI units.

a. Aluminium, 27 x 10^-3 kg/cm^3
b. Alcohol, 0.81 g/cm^3

Answer 1

International units for density correspond to

`\rho = (kg)/(m^3)`

For the first case we must convert the cubic centimeters to cubic meters and for the second case both the mass and volume units.

Remember that

`1000g = 1kg`

`1cm^3 = 1*10^(-6) m^3`

PART A) Aluminum

`\rho = 27*10^(-3) (kg)/(cm^3)((1cm^3)/(1*10^(-6)m^3))`

`\rho = 27000(kg)/(m^3)`

PART B) Alcohol

`\rho = 0.81(g)/(cm^3) ((1kg)/(1000g))((1cm^3)/(1*10^(-6)m^3))`

`\rho = 810(kg)/(m^3)`