Explain the formation of concave and convex surface liquid on the basis of molecular forces

It is observed that when a free surface of a liquid comes in contact with a solid, it shows a curvy shape near the point of contact. Here an inward depression or an outward bulging takes place. This is called the meniscus of a liquid.

It is caused by surface tension. It can be either convex or concave.

• A convex meniscus occurs when the molecules have a stronger attraction to each other (cohesion) than to the material of the container (adhesion).

• A concave meniscus occurs when the molecules of the liquid attract those of the container's, causing the surface of the liquid to cave downwards.
  
  Water wet the surface while mercury will not wet the surface

  Meniscus of water is concave while meniscus of mercury is convex because :

• A convex meniscus occurs when the molecules of the liquids have a stronger attraction to each other (cohesion) than molecule-container attraction (adhesive forces). In mercury the molecules have stronger cohesive force so we see convex meniscus.

• A concave meniscus occurs when the inter-molecular interaction of the liquid is less than that of the liquid-container attractive forces. Example: water molecules have less stronger cohesive forcers so we see a concave meniscus.