Name: Angle of Contact
Uploaded: 2019-07-19
Duration: 6 min 57 s
Description: What is the contact angle? Which factor does the contact angle depend on? Why does the contact angle for the same liquid on different surfaces differ? Let's...

Question

What are cohesive and adhesive forces? Explain the difference between them.

Accepted Answer

Cohesive force or force of cohesion- -It is the force of attraction amongst the molecules of the same substance. Definite shape and size of the solid is due to strong force of cohesion amongst their molecules.

Adhesive force or force of adhesion- -It is the force of attraction acting between the molecules of different
substances. For example, Water wets the surface of glass container. This is due to the adhesive force between water and glass molecule, which is more than the cohesive force between the water molecules.

Difference between adhesive and cohesive forces

$1 .$ Adhesive force happens between two dissimilar molecules or substances.

$\to$ When two similar substances or molecules face the force of attraction this force is known as cohesive force.

$2 .$ Adhesive force is generally the force of attraction present between the water molecules and the walls of xylem vessels.

$\to$ Cohesive force is rampant among water molecules.

$3 .$ Capillary action and meniscus (the curved surface which is formed by any liquid in a cylinder) are the effects of adhesive force

$\to$ Surface tension, meniscus and capillary action are the effects cohesive force.

$4 .$ Adhesive force is caused by electrostatic or mechanical forces that exist among two kinds of different substances.

$\to$ Cohesive force is caused by hydrogen bonding and Van der Waals forces.

$5 .$ A strong adhesive force causes the liquid to spread all over the surface.

$\to$ A strong force of cohesive forms water droplets on any surface.

What are cohesive and adhesive forces? Explain the difference between them.

Important Questions on Surface Tension

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