Evaporation of liquids : Different types of Evaporation : What is Evaporation of liquids

 Evaporation of Liquids:

                                        We observed that water and other liquids start to boil if they are heated to their boiling temperatures. The liquid starts to transform into vapors but the change of liquids into vapors goes on even when the temperature is below the boiling point. For example, A spread wet cloth being exposed to the air becomes dry in a short time due to evaporation of water. Water left in an open dish also disappears due to evaporation.

    The process by which a liquid slowly changes into its vapors at any temperature (below its boiling point) without the aid of an external source of heat is called the evaporation of liquids.

                Experiments have shown that the evaporation of liquids depends on the following factors.

1. Nature of liquid:

                    Liquid with low boiling points evaporates more rapidly than those with higher boiling
points. For example, the rate of evaporation of alcohol is higher than that of water.

2. Temperature of liquid:

                     Due to higher temperature, molecules of liquid at the surface will have more kinetic energy and chances of escaping will increases and evaporation will be fast. This can be seen while ironing clothes. Under a hot iron wet clothes dry out quickly as the water evaporates quickly.

3. Temperature of surroundings:

                    The higher the temperature of the surroundings, the higher the rate of evaporation. It is for this reason that wet clothes dry more rapidly in summer than in winter.

4. Presence of water vapor in Air:

                     The more the amount of water vapor present in the air, the less the rate of evaporation. It is for this reason that wet clothes dry slowly in the rainy season as a lot of water vapor are present in the air.

5. Area of the exposed surface of the liquid:

                     The increased surface area gives the molecules a greater chance of escaping. Wet roads dry out quickly because the rainwater is spread over a large area.

6. Movement of Air:

                      The more rapid the flow of air, the higher the rate of evaporation. It is for this reason that wet clothes dry more rapidly on a windy day compared to a calm day.

7. Dryness of Air:

                          The drier the air, the more rapid is the evaporation. The presence of water vapor reduces the rate of evaporation. Desert room coolers are more effective in cooling by evaporation in the dry month of June than it is in the humid month of August.