Which of the following statements is not true about surface tension ?

Options

A. A small liquid drop takes spherical shape due to surface tension.
B. Surface tension is a vector quantity
C. Surface tension of liquid is a molecular phenomenon
D. Surface tension of liquid depends on length but not on the area

Explanation

To determine which statement about surface tension is not true, let's analyze each option step by step.

### Step-by-Step Solution:

1. **Statement Analysis**:
- **Statement 1**: "A small liquid drop takes spherical shape due to surface tension."
- **Explanation**: This statement is true. A small liquid drop forms a spherical shape because surface tension acts to minimize the surface area. The cohesive forces between the molecules cause the drop to adopt a shape that has the least surface area for a given volume, which is a sphere.

2. **Statement 2**: "Surface tension is a vector quantity."
- **Explanation**: This statement is not true. Surface tension is a scalar quantity, not a vector. While it has a magnitude, it does not have a specific direction associated with it. Surface tension is defined as the force per unit length acting along the surface of a liquid.

3. **Statement 3**: "Surface tension of a liquid is a molecular phenomenon."
- **Explanation**: This statement is true. Surface tension arises from the intermolecular forces between liquid molecules. The cohesive forces between the molecules at the surface lead to the phenomenon of surface tension.

4. **Statement 4**: "Surface tension of liquid depends on length but not on area."
- **Explanation**: This statement is true. Surface tension is defined as the force acting along the surface per unit length (σ = F/L). It does not depend on the area of the surface but rather on the length of the line along which the force acts.

### Conclusion:
The statement that is not true about surface tension is **Statement 2**: "Surface tension is a vector quantity."

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