Evaporation
. Evaporation, gradual change of state from liquid to gas that occurs at a liquid’s surface. Examples of evaporation include rainwater evaporating from warm pavement after a thunderstorm and wet paint drying as solvents in the paint evaporate. Fingernail polish also hardens as acetone evaporates from the liquid polish. A liquid is made up of atoms or molecules (bound groups of atoms) that are in constant motion, traveling at different speeds. The average speed of these particles depends only on the liquid’s temperature. If the particles have enough energy, fast-moving particles striking other particles near the liquid’s surface may impart enough speed, and therefore enough kinetic energy (energy of motion) to cause the surface particle to leave the liquid and become gas atoms or molecules. The particle’s kinetic energy is directly related to its speed. As particles with the most kinetic energy evaporate, the average kinetic energy of the remaining liquid decreases. In a similar way, ...