In the last experiments described we had to make two measurements to find the density, namely, a mass and a volume. Now we can always measure mass more accurately than volume, and so, in the accurate determination of density, scientists
have overcome the necessity to measure volume (hence eliminating one source of errQ[) by using the idea of relative density The relative density of a substance is the ratio of the mass of any volume of it to the mass of an equal volume of water, or
re Venetian density Note that relative density has no units: it is simply a number or ratio. On the other hand, density is expressed in kg/m ‘ (SI unit) or gjcm3 (sub-multiple SI unit).