What is evaporation? Explain it on the basis of molecular motion.
EVAPORATION: “The change of liquid into its vapours at all temperature from its surface is called evaporation.”
EXPLANATION OF EVAPORATION on the bases of molecular motion:
Molecules of liquid have more spaces, the less molecular force of attraction and more K.E. than molecules of solids and can move throughout the liquid.
While moving they can not escape the surface as they are being pulled inside by other molecules as there are no molecules above the surface. But when some molecules acquire sufficient K.E. (Threshold velocity), they overcome the ATTRACTIVE FORCES of other molecules and escape into the open space above the liquid. These escaping molecules form the vapour of the liquid and the process called Evaporation continues till all the liquid evaporates.