Question

A liquid does not wet the surface of a solid, if the angle of contact is

• A. Zero
• B. Obtuse (more than ${90}^{\circ })$
• C. Acute (less than ${90}^{\circ })$
• D. ${90}^{\circ }\left(\text{right angle}\right)$

Answer 1

The correct option is B Obtuse (more than ${90}^{\circ })$

When the contact angle is obtuse (more than ${90}^{\circ })$, $\text{cohesive forces}>\text{adhesive forces}$, hence the liquid beads up.

If angle of contact is less than ${90}^{\circ }$, the liquid tends to spread at the solid surface. As the angle of contact becomes smaller, spreading of the liquid over the solid surface increases.


So the correct answer is $B$.