Capillary rise of water in a narrow glass tube occurs because
- A. the adhesive forces between water and glass are stronger than the cohesive forces within water
- B. the cohesive forces are stronger than the adhesive forces
- C. the air pressure inside the tube is greater
- D. water is denser than glass
Explanation
Water wets glass because it is attracted to the silica surface more strongly than to itself, so it climbs the walls and drags a column up, forming a concave meniscus. Mercury shows the opposite behaviour, with stronger cohesion, so it is depressed in the tube and forms a convex meniscus. The narrower the tube, the higher the rise.