Definition

1. Noun:
   • The pressure exerted by a vapor: This is the pressure that a vapor (the gaseous phase of a substance) exerts on its surroundings when it is in a closed container. It is a measure of the tendency of molecules to escape from the liquid or solid phase into the gas phase.
   • Saturated vapor pressure: Often, the term specifically refers to the equilibrium pressure exerted by a vapor that is in contact with its own liquid or solid form at a given temperature. At this point, the rate of evaporation equals the rate of condensation.

Usage Examples

• Noun:
  • The vapour pressure of water increases with temperature. (This describes how the pressure of water vapor in equilibrium with liquid water becomes higher as it gets warmer.)
  • Engineers must consider the fuel's vapour pressure for safe storage. (This indicates the pressure exerted by the fuel's vapor, which is a key safety and performance parameter.)
  • When the vapour pressure equals the atmospheric pressure, the liquid boils. (This explains the condition for boiling, using the concept of saturated vapor pressure.)

Advanced Usage

• "Lowering of vapour pressure": A colligative property where adding a non-volatile solute to a solvent reduces the solvent's vapour pressure.
  • The lowering of vapour pressure explains why saltwater boils at a higher temperature than pure water.
• "Equilibrium vapour pressure": A more precise term emphasizing the dynamic equilibrium between evaporation and condensation.
  • The equilibrium vapour pressure is constant for a given substance at a fixed temperature.

Variants and Related Words

• Vapor pressure: The American English spelling of "vapour pressure."
• Saturation vapor pressure: A synonym often used in scientific contexts.
• Partial pressure: In a mixture of gases, the contribution to the total pressure made by one specific gas; the vapour pressure of a substance is its partial pressure when the vapor is in equilibrium with its condensed phase.

Synonyms

• Saturated vapor pressure (in its specific sense).
• Equilibrium vapor pressure.

Related Scientific Concepts

• Boiling point: The temperature at which a liquid's vapour pressure equals the external pressure.
• Volatility: A qualitative term describing a substance with a high vapour pressure at room temperature.
• Raoult's Law: A law stating that the partial vapour pressure of a solvent in a solution is proportional to its mole fraction.

Noun

1. the pressure exerted by a vapor; often understood to mean saturated vapor pressure (the vapor pressure of a vapor in contact with its liquid form)