Vapor

Definition

Vapor is the gaseous phase of a substance that is typically liquid or solid under standard conditions. It forms when the substance undergoes a phase change due to heating or pressure reduction.

5 Must Know Facts For Your Next Test

1. Vaporization is the process through which a liquid turns into vapor, either by evaporation (at the surface) or boiling (throughout the bulk).
2. The temperature at which a liquid boils and turns into vapor is called its boiling point, dependent on atmospheric pressure.
3. Saturated vapor is in equilibrium with its liquid phase; any addition of heat will cause condensation rather than temperature increase.
4. Superheated vapor occurs when vapor exists at a temperature higher than its boiling point without condensing.
5. The relationship between pressure and volume of vapor can be described by the Ideal Gas Law: $PV = nRT$.

Review Questions

• What are the two main processes through which liquids turn into vapor?
• How does atmospheric pressure affect the boiling point of a liquid?
• What defines superheated vapor and how does it differ from saturated vapor?

Related terms

Boiling Point: The temperature at which a liquid's vapor pressure equals atmospheric pressure, causing it to turn into vapor.

Evaporation: The process where molecules at the surface of a liquid gain enough energy to enter the gaseous phase.

Condensation: The process where water vapor cools and changes back into liquid droplets.