Vapor
Vapor (British English: vapour) is when small drops of liquid float in the air. Sometimes this happens because the liquid has been heated. Vapor is not the same as gas. It is a mixture of liquid and gas. The usual word for this is steam.
Vapor Media
An ampule of nitrogen oxide vapor: brown nitrogen dioxide and colorless dinitrogen tetroxide, in equilibrium
The vapor-liquid critical point in a pressure-temperature phase diagram is at the high-temperature extreme of the liquid–gas phase boundary (the dotted green line gives the anomalous behaviour of water).
Liquid–vapor equilibrium
If the vapor pressure exceeds the equilibrium value, it becomes supersaturated and condenses on any available nucleation sites e. g. particles of dust. This principle is used in cloud chambers, where particles of radiation are visualized because they nucleate formation of water droplets.
Invisible water vapor condenses to form visible water droplets called mist
