a short knowledge of cohesion and adhesion differences

1. By Samjhana Thapa
Cohesion and Adhesion

2. Cohesion
 Attraction between same molecules - Like water is attracted to water
molecules
 Hold hydrogen bond together to create surface tension

3. Some examples of cohesion
Insect walk on water
Water droplet before falling down
Glass is fill up with
water beyond top
Oil drops falling down

4. Adhesion
 Attraction between different molecules- water molecules
stick to other substances
 Attraction can be due H-bond, polar attraction, dipole-dipole
attraction

5. Some examples of adhesion
water droplets at the tip of leafs
Water drops at the spider web

6. Capillary action
It occurs when adhesive forces is stronger than cohesive force
• concave miniscus in water
•Convex miniscus in mercury

7. Importance of cohesion and adhesion
 helps to transport water in plants
 Important role in water based process including movement
of water to top of trees and drainage of tears from tear duct
in corner of eyes

8. Differences between adhesion and cohesion
Adhesion
- Attraction in same molecule - Attraction between different
molecule
-caused by hydrogen bonding and
vander walls
-caused by electrostatic force
-strong force of cohesion cause water
droplet to form on any surface
- Strong force of adhesion cause
liquid to spread on solid surface