Find out from this experiment

If water is poured on a glass slab, the glass becomes wet; but if mercury is poured on the same glass surface it does not become wet. Why?

Whether a surface gets wet or not depends on

 1. The force of attraction between the molecules of the liquid and the molecules of the surface with which it is in contact, and

2. The cohesive force between the molecules of the liquid.

In the case of mercury, its molecules hold on tightly to each other. The molecules of the glass surface cannot pull them away. So the surface does not get wet.

In the case of water, the adhesive force is greater than the cohesive force between the water molecules. So the water clings to the glass surface, wetting it.

Picture Credit : Google 

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