Adhesion and cohesion

Cohesion

The force of attraction between the molecules of the same substances is called cohesion

Adhesion

The force of attraction between the molecules of different substances is called adhesion

  Example of adhesion and cohesion is found in water and glass,when water is spilled on the surface of a glass. The adhesion between water and glass is stronger than the cohesion between the water molecules

The cohesion of mercury is stronger than its adhesion with glass. Mercury forms small ball on the surface of glass

These are the reasons why the water surface is always concave to the air while mercury surface always concave to the mercury whenever they are in glass tube. see figure above.

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