Correct Answer - D
Another way that surface tension manifests itself is in capillary action. Two types of forces bring about capillary action. One is the intermolecular attraction between like molecules called cohesive forces). The other, which is called adhension , is an attraction between unlike molecules (the forces of attraction between a liquid and another surface are adhesive forces).
The partial positive charges on the `H` atoms of water bond strongly to the partial negative charges on the oxygen atoms at the surface of the glass (glass is mainly silica). As a result , water adherse to glass , or is said to wet glass. As water creeps up the side of the glass tube, its favorable area of contact with the glass increases. The surface of the water , its meniscus, has a concave shape. On the other hand , mercury does not wet glass because its cohesive forces (due to dispersion forces) are much stronger than its attraction to glass. Thus, its meniscus is convex.
Capillary action occurs when one end of a capillary tube [a glass tube with a small bore (inside diameter)] is immersed in a liquid. If the adhesive forces exceed the cohesive forces, the contents of the tube will be pulled upward along the walls , i.e., the liquid creeps up the sides of the tube . This process continues until the adhesive forces are balanced by the weight of the liquid in the tube. This action is by no means universal among liquids. In mercury , cohension is greater than adhersion between mercury and glass , so that a depresssion in the liquid level actually occurs when a capillary is dipped into mercury.
