Question

(a) Write any two differences between boiling and evaporation.
(b) How does evaporation cause cooling?

Answer 1

Both evaporation and boiling are a kind of thermodynamic process that includes exchange of heat energy between the system and the surrounding. Both of the processes are very common and are both a part of our everyday life.

Complete Step by step answer:
(a)Difference between evaporation and boiling:

Evaporation	Boiling
It is the process to convert water which is in liquid state, to its vapor form, that is to gaseous state. This is a natural procedure. It happens very slowly.	Boiling is conversion of water to its vapor form or conversion of liquid to gaseous state. It is not a natural procedure and happens very quickly.
The process of evaporation takes place by the virtue of increase in temperature or change in the pressure. It always takes place on the topmost surface of liquid.	2. It occurs on account of heating when heat is given continuously from outside and it happens via the medium and water molecules after it is heated up and rises to top, from bottom.
As we know, evaporation is a slow process, so there is no visible indication in the medium where evaporation is occurring.	3. As we know that boiling is a very rapid process, a visible differentiated sign is the bubble effect on the top layer surface of water, occurring at boiling point.

(b) In evaporation the molecules from water absorb energy from the surrounding and elevate their own internal energy. Now these molecules with high energy start to collide more often and try to escape the surface of liquid. This phenomenon of absorbing energy from surroundings causes a cooling effect. This sort of property of evaporation is observed during natural water cooling.

Note: The process of evaporation occurs naturally, so it can occur at any temperature but boiling point needs a particular minimum temperature to hold for it to take place. Evaporation is often confused with transpiration. Transpiration occurs on the leaf surface, where water is given out from the stomata of the leaf with help of evaporation.