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.

The correct answer is: Statement-I is false but Statement-II is true.

Let us analyze each statement carefully using the principles of capillarity and surface tension.

Analyzing Statement-I:

The height to which a liquid rises (or falls) in a capillary tube is given by the well-known formula:

h=\frac{2Tcos\theta }{\rho gr}

where T is the surface tension of the liquid, θ is the contact angle, ρ is the density of the liquid, g is the acceleration due to gravity, and r is the radius of the capillary tube.

For the liquid to neither rise nor fall, we need h = 0. This requires:

cos\theta =0\Rightarrow \theta =90°

Now, if the contact angle were θ = 0°, then:

cos0��=1\Rightarrow h=\frac{2T}{\rho gr}>0

This gives the maximum possible capillary rise — not zero. So the liquid would definitely rise in the capillary tube when the contact angle is 0°. Therefore, Statement-I is FALSE.

Analyzing Statement-II:

The contact angle (θ) at a solid-liquid interface is determined by the balance of three interfacial tensions — the solid-liquid, solid-vapor, and liquid-vapor surface energies — described by Young's equation:

cos\theta =\frac{{\gamma }_{sv}-{\gamma }_{sl}}{{\gamma }_{lv}}

Each of these surface energy terms depends on the specific material of the solid and the specific material of the liquid in contact. For example:

• Water on glass: θ ≈ 0° (wetting, liquid rises)
• Mercury on glass: �� ≈ 135° (non-wetting, liquid depresses)
• Water on a wax surface: θ > 90° (hydrophobic behavior)

This clearly shows that the contact angle is an intrinsic property of the solid-liquid pair — it changes depending on what material the solid is and what material the liquid is. Therefore, Statement-II is TRUE.

Conclusion:
Statement-I is false (a contact angle of 0° causes maximum rise, not zero rise — the angle must be 90° for no rise or fall).
Statement-II is true (the contact angle is indeed a material property of both the solid and the liquid involved).