In general, a vapor phase consists of a phase with two different substances at room temperature, whereas a gas phase consists of a single substance at a defined thermodynamic range, at room temperature. Thus, this is defined as the key differences between Vapor and Gas. You can find the major differences in the table below.
|Vapour is a mixture of two or more different phases at room temperature, these phases are liquid and gaseous phase.||Gas usually contains a single thermodynamic state at room temperature.|
|Vapour has a definite shape of the gaseous particles when observed under a microscope.||Gas does not a definite shape when it is observed under a microscope.|
|Vapour consists of random molecules and atoms moving randomly about.||Gas also consists of random molecules and atoms moving about randomly.|
|Vapour is not a state of matter, unlike gases.||Gases are a state of matter.|
|Vapours of water are around us all the time at temperatures below the boiling point of water.||Gases are usually formed above its critical temperature, but below critical pressure.|
For liquid, it have a definite volume, but take the shape of the container. The gases have no definite shape or volume.