Density Y = = 3 g/mLAll this means is that every 1 mL of substance X weighs 4 grams, and every 1
mL of substance Y weighs 3 grams. So, for this example, 5 mL of X weighs 20
grams, and 15 grams of Y occupies a volume of 5 mL.
At a given temperature, a certain mass of a substance that is a solid or a liquid
has a fixed volume. This means that for liquids and solids at a given temperature,
density does not vary. The same is not true of gases. A sample of any gas will
expand to fill its container. We can double the volume of the container without
changing the mass of the sample of the gas, and the density will decrease by a
factor of two.