If a glass rod is dipped in mercury and withdrawn out, the mercury does not wet the rod because

Options

A. Angle of contact is acute
B. Cohesion force is more
C. Adhesion force is more
D. Density of mercury is more

Answer

To solve the question of why a glass rod does not get wet when dipped in mercury and withdrawn, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding Cohesion and Adhesion:**
- **Cohesion** refers to the intermolecular forces that attract like molecules to each other. In the case of mercury, the molecules are strongly attracted to each other.
- **Adhesion**, on the other hand, refers to the forces of attraction between unlike molecules, such as those of mercury and glass.

2. **Comparing Forces:**
- In the case of the glass rod and mercury, we need to compare the cohesion forces (between mercury molecules) and the adhesion forces (between mercury and glass molecules).
- The cohesion forces in mercury are significantly stronger than the adhesion forces between mercury and the glass rod.

3. **Resulting Behavior:**
- Because the cohesion forces are stronger, mercury tends to pull itself together rather than spreading out to wet the glass rod.
- This results in the mercury forming a bead on the surface of the glass rod instead of spreading out and wetting it.

4. **Conclusion:**
- Therefore, when the glass rod is withdrawn from the mercury, it does not get wet because the cohesive forces of mercury dominate over the adhesive forces between the mercury and the glass.

### Final Answer:
The glass rod does not get wet when dipped in mercury because the cohesive forces between mercury molecules are stronger than the adhesive forces between the mercury and the glass rod.

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