Question

Explain why the angle of contact of mercury with glass is obtuse while that of water with glass is acute.

Answer 1

The angle made by the mercury from the glass surface is always obtuse. The adhesive force between the molecules of glass and water is more than the cohesive force between the molecules of water.This results in the formation of a concave meniscus for the surface of water

Answer 2

Hey mate,

◆ Angle of contact-
It's the angle between tangent to the liquid surface at point of contact & the solid surface inside the liquid.

◆ Angle of contact of mercury with glass is greater than that of water because -
- For mercury, cohesive force between mercury molecules is greater than adhesive force with glass surface, therefore mercury drop appears more bulged and has obtuse angle of contact.
- For water, cohesive force between water molecules is lesser than adhesive force with glass surface, therefore water drop appears flat and has acute angle of contact.

Hope this is helpful...