Is surface tension effected by impurities?
The presence of impurities either on the surface or dissolved in it, affect surface tension of the liquid. Highly soluble substances increase the surface tension of water, whereas sparingly soluble substances reduce the surface tension of water.
The surface tension of a liquid decreases with increase in temperature. The surface tension of a liquid becomes zero at its boiling point and vanishes at critical temperature.
Surface tension is the property of a liquid which resists deformation of its surface. A surface exerts a force outward and perpendicular to the surface when it is being deformed. The surface tension is the energy per unit area necessary to create a larger surface area of a liquid. The cause of surface tension is the cohesive (polar) forces between molecules in the liquid. See related questions and links.