Advertisements
Advertisements
Question
Comment on the statement ‘evaporation is a surface phenomenon’.
Advertisements
Solution
-
Particles at the Surface Escape:
- In a liquid, particles at the surface are loosely bound compared to those inside.
- When surface particles gain enough energy (e.g., from heat), they overcome the forces of attraction and escape into the air as vapor.
-
No Boiling Required:
- Unlike boiling, evaporation happens at any temperature below the boiling point and does not require heating the entire liquid.
- Only the particles at the surface participate in evaporation.
-
Examples:
- Water in a glass slowly evaporates from the surface over time.
- Sweat on the skin evaporates, cooling the body.
APPEARS IN
RELATED QUESTIONS
Evaporation takes place only from the surface of liquid.
Boiling occurs at ....................
The molecules of liquid ............. heat from surroundings in evaporation.
Heat is ................... during boiling.
Match the column
| Column A | Column B |
| (a) Blowing air increases | (1) Increase in intermolecular separation |
| (b) Increase in pressure increases | (2) Pendulum of a clock |
| (c) Thermal expansion |
(3) Cooking utensils |
| (d) Invar | (4) Boiling point |
| (e) Pyrex glass | (5) Evaporation |
During boiling or vaporization
Give reason for the increase in rate of evaporation of a liquid when air is blown above the liquid.
Give reason for the increase in rate of evaporation of a liquid when surface area of liquid is increased.
What is the change in average kinetic energy of molecules of a liquid during boiling at its boiling point?
Name two ways of change of liquid state to the vapour state and distinguish them.
