The Macroscopic View
Condensation is the change from a vapor to a condensed state (solid or liquid). Evaporation is the change of a liquid to a gas.
The Microscopic View of Condensation
|Microscopic view of a gas.
|Microscopic view after condensation.
When a gas is cooled sufficiently or, in many cases, when the pressure on the gas is increased sufficiently, the forces of attraction between molecules prevent them from moving apart, and the gas condenses to either a liquid or a solid.
The Microscopic View of Evaporation
|Microscopic view of a liquid.
|Microscopic view after evaporation.
When a liquid is heated sufficiently or when the pressure on the liquid is decreased sufficiently, the forces of attraction between molecules do not prevent them from moving apart, and the liquid evaporates to a gas.