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

$\rho = \frac{kg}{m^3}$

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

$\rho = 27*10^{-3} \frac{kg}{cm^3}(\frac{1cm^3}{1*10^{-6}m^3})$

$\rho = 27000\frac{kg}{m^3}$

PART B) Alcohol

$\rho = 0.81\frac{g}{cm^3} (\frac{1kg}{1000g})(\frac{1cm^3}{1*10^{-6}m^3})$

$\rho = 810\frac{kg}{m^3}$