Question

Define angle of contact of a liquid with a solid surface. Why does it vary for different liquids?

Answer 1

Angle of contact in fluids is referred to as the angle between the tangent to the liquid surface and the horizontal or simply it is an angle that is made by the tangent drawn to the meniscus from the point of contact with the walls of the container in which the liquid is kept. Angle of contact varies with the atmospheric pressure, adhesive and cohesive forces of the liquid in the tube.

Now, the angle of contact is different for different liquids because, as different liquids have different densities and forces of attraction, the adhesive and cohesive forces would also be clearly different. And as the angle of contact depends upon the adhesiveness and cohesiveness of the forces, it varies with different liquids.