Correct Answer - Option 4 : decreases with the increases in temperature
CONCEPT:
Surface tension:
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Surface tension is the tension of the surface film of a liquid caused due to the attraction of the particles in the surface layer by the bulk of the liquid, which tends to minimize surface area.
- It is defined as the ratio of the surface force F to the length L along which the force acts.
\(\Rightarrow T=\frac{F}{l}\)
Where T = surface tension
- When impurities are added to the water the intermolecular distance increases due to which van der wall forces decrease, so the surface tension decreases on adding impurities to the water.
EXPLANATION:
- Surface tension is given as,
\(\Rightarrow T=\frac{F}{l}\) -----(1)
- By equation 1 it is clear that the surface tension does not depend on the area.
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Surface tension decreases with the increase in temperature.
- The decrease of surface tension with an increase in temperature results because of the kinetic energy (or speeds) of the molecules increases. Thus, the strength of intermolecular forces decreases resulting in the decrease of the surface tension.
- Hence, option 4 is correct.
