Evaporation and Boiling

The molecules in a liquid are at random motion. In the random motion, the different molecules have different velocities and hence different kinetic energies. In addition, the molecules of the liquid collide with each other. They may exchange their kinetic energies in the collisions. In the collisions, some of the liquid molecules may get energy enough to be converted into vapour even at low temperature.The conversion of some of the liquid molecules into even blow the boiling point is called evaporation. When evaporation takes place, the molecules which fly off the body of the liquid take the required energy for the evaporation from the remaining molecules of the liquid. Since the kinetic energy of the remaining molecules has been decreased,there is net fall in temperature of the liquid. Thus,cooling is resulted from the evaporation of a liquid.
The evaporation of liquid can be defined as slow and silent conversion of the liquid from its liquid state to gaseous state at all temperature.
It has been found that the rate of evaporation of a liquids depends upon the following:

• Nature of the liquid .
• Temperature of liquid.
• Area of the surface of the liquid.
• Pressure and temperature of the atmosphere.
• Effect of liquid.
• Humidity of the atmosphere.

However, the boiling (also called equilibrium) is a rapid and noisy conversion of a liquid into vapour at a particular temperature called boiling point.The temperature of the liquid does not change during boiling. No cooling effect is observed.