Question

Given below are two statements :
Statement-I: When a capillary tube is dipped into a liquid, the liquid neither rises nor falls in the capillary. The contact angle may be 0°.
Statement-II: The contact angle between a solid and a liquid is a property of the material of the solid and liquid as well : In the light of above statement.
Choose the correct answer from the options given below.

• A. Statement-I is false but Statement-II is true.
• B. Both Statement-I and Statement-II are true.
• C. Both Statement-I and Statement-II are false.
• D. Statement-I is true and Statement-II is false.

Answer 1

The Correct Option is A

Capillary rise is given by:

\[ h = \frac{2T \cos \theta}{\rho g r} \]

If \(\theta = 0^\circ\), the rise is non-zero, so Statement-I is incorrect. Statement-II is correct as the contact angle depends on the materials involved.

Answer 2

Step 1: Analyze Statement-I
Statement-I says that when a capillary tube is dipped into a liquid, the liquid neither rises nor falls, and the contact angle may be \(0^\circ\).
However, this is incorrect. The liquid neither rises nor falls only when the angle of contact \(\theta = 90^\circ\), because in that case the adhesive and cohesive forces balance exactly. When \(\theta = 0^\circ\), capillary rise is maximum (for example, water in a clean glass tube).
Hence, Statement-I is false.

Step 2: Analyze Statement-II
Statement-II says that the contact angle between a solid and a liquid depends on the nature of both the solid and the liquid. This is correct because the contact angle is determined by the molecular interaction between the solid surface and the liquid (adhesive and cohesive forces).
Therefore, Statement-II is true.

Step 3: Conclusion
Statement-I is false, but Statement-II is true.

Final answer

Statement-I is false but Statement-II is true.