Different gases exhibit varying densities due to differences in their molecular masses, despite the absence of intermolecular attractions. Density, defined as mass per unit volume, indicates that either the mass or volume must differ for gases to have distinct densities. The discussion highlights the relationship between gas identity, volume, and the ideal gas law, which states that for a fixed number of moles at constant pressure and temperature, the volume of a gas is influenced by its molecular mass. Thus, while the ideal gas approximation allows for generalizations, the specific identity of the gas does affect its volume under these conditions.