Vapour
What is Vapour?
Vapour (vapor) is the gaseous phase of a substance that normally exists as a liquid or solid at room temperature, present below the critical temperature of the substance. Unlike a true gas (which is above its critical temperature), a vapour can be condensed to a liquid by increasing pressure alone without cooling. Vapour pressure — the pressure exerted by the vapour in equilibrium with its liquid — is a key thermodynamic property that determines volatility, boiling point, and evaporation rate.
Key Facts
Frequently Asked Questions
Vapour (vapor) is the gaseous phase of a substance that normally exists as a liquid or solid at room temperature, present below the critical temperature of the substance. Unlike a true gas (which is above its critical temperature), a vapour can be condensed to a liquid by increasing pressure alone without cooling. Vapour pressure — the pressure exerted by the vapour in equilibrium with its liquid — is a key thermodynamic property that determines volatility, boiling point, and evaporation rate.