Which is a physical property of a gas?

Physical property of gas: There are a lot, here are some examples: => Air => Oxygen => Carbon dioxide => Flourine => Phosphine => Argon => Carbon monoxide This examples are all gases and each of these gases has its own physical property. The only thing that they makes them the same are that, they are gas with lesser molecules. Usually gas density is lesser compare to the solid or liquid and most gases has undefined melting point.