To use the known mass of a substance to calculate the volume occupied by that substance, divide the mass by the density of the substance. The units in which density is expressed must be the same as those used to measure mass and the volume.
Step 1: Obtain density and convert units if needed.
Convert the units used for mass in the density to mg and the units used for volume to cm3.
Step 2: Modify density to account for the temperature and pressure, if needed.
The density of most substances is affected in some way by temperature and pressure. Fortunately, these changes are negligible for substances in a liquid or solid state and can be ignored. However, when the substance in question is a gas, temperature and pressure are essential components of density and the correct density will need to be calculated based on the Ideal Gas Law.
Step 3: Divide the mass of the substance by the density of the substance.