Answer :
Final answer:
Mercury descends in a glass capillary tube because its cohesive forces are stronger than adhesive forces to glass, resulting in a convex meniscus and a downward force that suppresses the mercury in the tube.
Explanation:
When a glass capillary tube is dipped into mercury, the behavior of the mercury is dictated by the surface tension and adhesive and cohesive forces at play. The adhesive forces between the glass and mercury are weaker compared to the strong cohesive forces within the mercury itself. This results in a convex meniscus, and consequently, the mercury descends in the capillary tube below the surface level of the surrounding mercury. This is the opposite of how water behaves in a glass capillary, where adhesive forces are stronger, resulting in a concave meniscus and capillary action that causes the water to rise.
