Illustrated Glossary of Organic Chemistry

Evaporate (evaporation): A phase change in which a liquid phase is converted to a gas phase. Particles in the liquid phase experience noncovalent molecular attractive forces, so evaporation requires disrupting (overcoming) these attractive forces. Evaporation can occur at any temperature; it does not require the liquid to be at its boiling point. (Evaporation is faster at the boiling point than at lower temperatures.) Evaporate (evaporation) is synonymous with vaporize (vaporization).

         
Distillation involves evaporation. A liquid is heated in flask 2 (which accelerates its evaporation). The vapors rise from the liquid's surface through column 3 (leaving impurities behind), and are then condensed back into the liquid phase in condenser 5 (the reverse of evaporation). The pure liquid collects in flask 8. The boiling point can be measured with thermometer 4.          








20 oC: Slower evaporation
100 oC: Faster evaporation
Evaporation of water occurs at any temperature, but is faster at 100 oC (water's boiling point) than at 20 oC (room temperature).






Sublimation is not the same as evaporation, because sublimation is a solid-to-gas phase change, whereas evaporation is a liquid-to-gas phase change. Click the image to watch a time-lapse sublimation of dry ice (solid carbon dioxide). Notice the lack of liquid accumulation.