Effects of Impurities and Temperature on Surface Tension.
I. Highly soluble impurities (like salt) tend to increase the surface tension of water.
II. Sparingly soluble impurities (like soap/phenol) tend to decrease the surface tension of water.
III. Increasing the temperature generally decreases the surface tension.
IV. At the critical temperature, surface tension becomes zero and the meniscus disappears.
V. Surface tension affects the saturation vapor pressure over a curved surface (Kelvin effect).
