The meniscus of mercury in a glass tube is convex because
- A. mercury is a metal
- B. mercury evaporates rapidly
- C. cohesive forces between mercury atoms exceed the adhesive forces to glass
- D. glass is polar and mercury is non polar
Explanation
Mercury atoms are held to each other by strong metallic bonding far more strongly than they are attracted to the glass, so the liquid pulls away from the walls and the surface bulges upwards. Water shows a concave meniscus for the opposite reason. When reading a burette or a thermometer the eye must be level with the bottom of a concave meniscus and the top of a convex one.