| GAS | VAPOUR | 
| Gas exists in gaseous state at room temperature | Vapour exists in equilibrium with solid or liquid state at room temperature | 
| It is a state of matter | It coexists with liquid or solid at room temperature | 
| The particles in gases do not have a proper arrangement when observed under the microscope | The particles in vapour arrange in a proper shape when observed under the microscope | 
| It appears at temperature greater than or equal to boiling point | It may occur at temperature below boiling point | 
| Gas can be liquified or solidified under high pressure and only under low temperatures | Vapour can be liquified or solidified under high pressure and ordinary temperatures | 
| Eg. Helium, Nitrogen | Eg. Water vapour, Iodine vapour | 
 
  
 
