What is Evaporation and boiling?
Last updated on April 17th, 2023 at 05:09 am
Evaporation: Evaporation is the process in which liquid changes to a vapour state. Evaporation occurs when heat energy forces the bonds which hold the water molecules to break, causing the water to shift from its liquid state to a gaseous state.
Boiling: Rapid vapourization of liquid when it is heated to its boiling point is known as boiling. The boiling point is the temperature at which liquid changes its state when the vapour pressure is equal to the atmospheric pressure. The boiling point of water is 100 degree Celsius at 1 bar pressure (atmospheric pressure)
Difference between evaporation and boiling
| Evaporation | Boiling |
| 1. Evaporation is a slow process. 2. It takes place on the surface. 3. It can take place at any temperature below boiling point. 4. It cannot form bubbles due to more atmospheric pressure on it | 1. Boiling is a fast process 2. Takes place throughout the volume. 3. At boiling point (in the case of water, it boils at 100 degree Celsius at 1 bar of pressure). 4. It forms bubbles and rises due to the increase of vapour pressure than atmospheric pressure |
What is Vapour pressure?
Vapour pressure: It is the pressure exerted by vapours of liquid on the surface of the liquid when equilibrium is established between liquid and its vapour is known as the vapour pressure of the liquid.
In fig (a) we can see that in the open container, evaporation is taking place, and water vapours are going out of the container. In fig (b) there is a lid placed upon the container due to which water vapours are not able to go out of the container, the water vapours hit the lid and turn back to the liquid and condensation takes place. When the rate of evaporation is equal to the rate of condensation happening it is said to be in equilibrium and this is known as vapour pressure.