Question

On which of the following factor, the surface tension of a liquid does not depend?
1. liquid temperature
2. nature of liquid
3. presence of impurity
4. area of the free surface

Answer 1

Correct Answer - Option 4 : area of the free surface

CONCEPT:​

• Surface tension: The property of liquid surfaces to shrink into the minimum surface area possible is known as surface tension.
• The surface tension of a liquid depends on temperature, impurity in the liquid, nature of the liquid, etc.

EXPLANATION:

• Liquid temperature: Surface tension of liquids decreases with an increase in temperature.
• Nature of liquid: On changing the liquid the surface tension will change. So it depends on the nature of the liquid.
• Presence of impurity: The surface tension of water increases when soluble impurities are added to it. 
  • Insoluble impurities like detergent decrease the surface tension
  • It has both effects depending on the impurity.
• Area of the free surface: Surface tension does not depend on the area of the free surface.
  • When the surface area of a liquid is increased, molecules are allowed to move from the bulk phase to the interface.
  • As a result, the number of molecules per unit area remains the same or the distance between the molecules at the interface.
  • Therefore, the surface tension does not change.
• So the correct answer is option 4.