On heating a liquid, its surface tension

Options

A. Increases
B. Decreases
C. Remains same
D. Is reduced to zero

Answer

**Step-by-Step Solution:**

1. **Understanding Surface Tension**: Surface tension is defined as the force that acts on the surface of a liquid, causing it to behave like a stretched elastic membrane. This phenomenon occurs due to the cohesive forces between liquid molecules.

2. **Cohesive Forces**: The cohesive forces are the intermolecular forces of attraction that hold similar molecules together. In a liquid, these forces are responsible for the liquid's surface tension.

3. **Effect of Temperature on Kinetic Energy**: When a liquid is heated, the temperature of the liquid increases, which in turn increases the kinetic energy of the molecules within the liquid.

4. **Impact on Intermolecular Forces**: As the kinetic energy of the molecules increases, the molecules move more vigorously, which leads to a decrease in the effective intermolecular forces of attraction. This is because the increased motion allows molecules to overcome some of the cohesive forces that hold them together.

5. **Conclusion on Surface Tension**: Since surface tension is directly related to the strength of the intermolecular forces, a decrease in these forces due to increased temperature results in a decrease in surface tension. Therefore, when a liquid is heated, its surface tension decreases.

**Final Answer**: On heating a liquid, its surface tension decreases.

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