The more energy molecules have, the faster they move, making it possible for them to break the bonds that hold them together. Evaporation occurs when the molecules of a substance have enough kinetic energy to escape from the substance's surface as vapor. The escaping molecules absorb heat energy from the remaining molecules and cause the substance to become cooler. Evaporation occurs more rapidly when temperature is increased. An increase in temperature increases the energy of a substance's molecules, enabling them to escape at a faster rate.
Different substances vary greatly in the speed at which they evaporate at a given temperature.
For example, alcohol, ammonia, and the anesthetic diethyl ether evaporate quickly when poured onto an open surface at room temperature. Such substances are said to be volatile. They are said to be nonvolatile. A substance that is nonvolatile at one temperature may become volatile if it is heated. In this sense, the boiling point of a substance is a measure of its volatility.