Question

A water proofing agent changes the angle of contact :

• A. from acute to $90^{\circ }$
• B. from obtuse to $90^{\circ }$
• C. from an acute to an obtuse angle
• D. from an obtuse to an acute angle

Answer 1

Answer: (C)

The angle inside the liquid between the tangent to the solid surface and the tangent to the liquid surface at the point of contact is called the angle of contact for that pair of solid and liquid. Water proofing agent reduces the adhesive forces, hence angle of contact changes from an acute angle to obtuse angle.