Which type of fluids have zero surface tension?

CONCEPT:

• Surface tension: The property by virtue of which liquid tries to minimize its free surface area is called surface tension.
• In spherical shape the surface area is minimum and for this reason, the raindrops are spherical.
• Two factors can affect the surface tension of a liquid. The factors are;
  • Temperature: If temperature increases then the surface tension of a liquid decreases.
  • Soluble Impurities: In the case of less soluble impurities, the surface tension decreases. But, for highly soluble impurities in the liquid, the surface tension increases.
• Examples:
  • When kerosene oil is sprinkled on the water the surface decreases and for this reason, the mosquito larvas die due to sinking in the water.
  • Warm soup is tasty because for high temperatures the surface tension becomes low and spread equally over the tongue.

EXPLANATION:

• Intermolecular force: The force between the molecules of the fluid is called intermolecular force
• The intermolecular force is responsible for the viscosity of the fluid. 
• If the intermolecular force is more then the viscosity will be more and if it is less then the viscosity will be less.
• Real fluids possess some finite value of surface tension because the real fluids have a significant value of the intermolecular forces between the molecules.
• Whereas in the case of an ideal fluid, the intermolecular forces are assumed to be very less that's why the ideal fluids have zero value surface tension. So option 2 is correct.
• Separation of oil and water takes place due to surface tension.