Adding heat to liquid can increase liquid vaporization until vapor pressure equals air pressure {boiling}|. Heating fluid makes bubbles. Bubbles are liquid vapor, not air bubbles. Boiling is only on pot bottom, because bottom is hottest.
Liquid-to-gas state change is at a temperature {boiling point}| and pressure.
Surface-molecule collisions make some molecules have enough energy to leave surface and make vapor, which has pressure {vapor pressure}|. Molecules that left liquid before can later fall back into liquid from vapor, so vapor pressure depends on outside pressure and temperature. Substances in liquid mixtures contribute partial pressure to total vapor pressure. Total vapor pressure equals sum of partial pressures. Mixed-liquid vapor pressure is less than pure-liquid vapor pressure. Vapor pressure equals mole fraction times pure-vapor pressure: P = f * P0.
State change from liquid to gas is easier if material has weaker bonds between molecules {volatility}|. Materials with small non-polar molecules, globular shape rather than linear shape, and small forces between molecules are volatile. Volatility is high if chemical potential is high. Solute amount that can vaporize depends on boiling point and vaporization enthalpy. If both are low, solute disrupts easily and leaves.
Vapor and liquid {azeotrope}| can have same composition, if they form third material or help each other dissociate.
Partial pressure equals substance mole fraction in liquid times total pressure {Dalton's law} {Dalton law}. Total vapor pressure equals sum of partial pressures.
Liquid can change to gas {vaporization}|. Vaporization causes drying. Liquid-to-gas state change is at a boiling point temperature and pressure. As liquid becomes gas, gas absorbs heat and cools surroundings, as in refrigeration and air conditioning.
Gas can change to liquid {condensation, gas}|. Gas-to-liquid state change is at a temperature {condensation point} and pressure. Cold surfaces cool nearby air and cause air to lose water, which forms surface droplets.
Solid can change to gas {sublimation, heating}|. Solid-gas state change is at a temperature {sublimation point} and pressure.
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Date Modified: 2022.0225