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 | Gas |
| 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.
