A liquid is an example of a fluid (apart from gas), and its composition is such that allows easy movement of its molecules. The molecules of a liquid are held together by cohesive forces which confines them within a restricted space. Each molecule possess different energy levels, and so, some are more energetic than the others. If the more energetic molecules come near the liquid surface, they can break away from the attractive forces of the other nearby molecules and escape into the air.
Thus, for any molecule to escape, it must be sufficiently energized at a particular temperature. Evaporation is simply the process that favors the escape of liquid molecules to becoming gaseous substances, occurring at a particular temperature. When a liquid evaporates, its molecules are unbounded from their former restricted state, and their overall kinetic energy increases greatly. Therefore, they will be able to move randomly without any restrictions.Evaporation of a liquid occurs at all temperatures but, the rate of evaporation increases with increase in temperature.
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