SURFACE TENSION

According to molecular concept of matter liquid is made of a large number of molecular.The molecules which are below the surface of liquid

are attracted from all directions those on the surface are attracted only towards the interior.Therefore, all the surface molecules experience resultant downward pull.

This force which exerts an inward pull on the molecules at the surface is called surface tension.Because of surface tension,the whole

surface behaves like a stretched elastic membrane under tension,which always tends to contract so as to keep the surface area minimum

The surface tension tends to reduce surface area of liquid as much as possible.This explains why the drop of the liquid assumes a spherical shape because a sphere has a minimum surface area for a given volume of the liquid

Energy is required to increase the surface area of liquid.The surface tension of a liquid is also the measure of the energy required to

increase the surface area by unit amount.Surface tension is defined as the force in dyneacting as aright angles to any line of a unit

length drawn on the surface of the liquid.It's units is dynes per cm in c.g.s units and newton per meter in SI units.

The greater the intermolecular force of attraction in a liquid, the greater will be its surface tension.The surface tension of water is

greater than of ethonal and ether.This mean that intermolecular force of attraction in water is stronger than in the case of ethonal

and ether.