The fluid property, due to which, mercury does not wet the glass is
1. surface tension
2. specific gravity
3. polarity
4. viscosity

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Detailed Explanation:

The correct answer is: 1. surface tension

Mercury’s refusal to wet glass is a classic example used in fluid mechanics and surface science. This phenomenon is primarily due to high surface tension and strong cohesive forces between mercury atoms.

What Is Surface Tension?

Surface tension is a fluid property that arises due to cohesive forces between liquid molecules. It causes the surface of the liquid to behave like a stretched elastic membrane.

In the case of mercury:

• Cohesive forces (between mercury atoms) are much stronger than the adhesive forces (between mercury and glass).

• This results in mercury forming spherical droplets on a glass surface rather than spreading out.

• The contact angle between mercury and glass is greater than 90°, indicating non-wettability.

Why Glass?

Glass is a polar material, and mercury is non-polar. The lack of interaction between them leads to poor adhesion. Thus, the liquid tends to pull away from the glass surface, demonstrating non-wetting behavior.

Comparison with Water:

Unlike mercury, water wets glass because the adhesive forces between water molecules and glass are stronger than water’s internal cohesive forces, resulting in spreading and wetting behavior.

Conclusion:

The reason mercury does not wet glass lies in its high surface tension, which causes strong cohesion among mercury atoms and weak adhesion to glass. This unique behavior highlights the importance of intermolecular forces in fluid dynamics and material interactions.