The surface tension is the property of a liquid which allows to resist the external force applied on the liquid surface. The cohesive force is responsible for the surface tension of the liquid, this force is present between the water molecules which helps to bond together. The object with the light weight like paperclip, razor blade, needle, small insects, etc. these objects can float on the liquid surface due to cohesive force present on the surface.

The surface tension can be observed in the spherical form, the water drop and the soap bubbles are the example if the spherical surface tension. The force of attraction present in the molecules of the water, it is attractive towards each other. The particular water molecule is attracted towards another water molecule in all the directions. The unit of the surface tension is Joules per square metre because the it is in the form of the energy or work. Normally the surface tension of the water is about 0.07275 Joules per square metre. Some of the liquid such as alcohol and Benzene has lower surface tension and some of liquid like mercury having the high surface tension.

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The surface tension establishes the barrier between the water and the outer atmosphere, surface tension can be understand by some examples which are given below:

1. The small insects can walk on the water surface very easily because the weight of the insects like spider is very low which can not penetrate the surface of the water.

2. When water drop falls on the leaf of the tree, because of the waxy surface of the leaf the surface tension of the water drop generates the spherical shape.

3. In the case of the vertical tube of the mercury barometer the upper shape of the mercury becomes dom - shaped because of the low diameter of the tube.

4. The warm water used to washing the cloths because the warm water having the lower surface tension than the cold water, because of this the detergent will be faster dissolved into it.

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When the object comes in the contact with the water surface that time the surface acts as a elastic material but the over weight applied on the surface the elastic property no longer present on the surface. The surface tension of the water and the sea water is different.