How does a liquid's vapour pressure affect its surface tension?

i.e. to say, if a liquid's vapour pressure increases, will the surface tension increase or decrease?

The SERP for this question yields only research papers to which I don't have access. This theory isn't given in my textbook either.

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    $\begingroup$ Your cause and effect is backward. A decreasing surface tension increases vapor pressure. though you ussually can't control surface tension as an independent variable. $\endgroup$ – A.K. Dec 9 '17 at 17:04
  • $\begingroup$ @A.K. Oh! Actually, in my test paper, the statement was "A liquid with low vapour pressure will have high surface tension ", that's why I had framed the question this way. But, what is the reason for "decreasing surface tension increases vapor pressure"? $\endgroup$ – Gaurang Tandon Dec 9 '17 at 17:08

High surface tension is caused by strong intermolecular forces, the same are responsible for a low vapour pressure.

It is however quite a different matter to put a molecule on a surface and to completely strip it from a condensed phase and put it into the gas phase. There sure is no (inverse) proportionality or similar between vapour pressure and surface tension, and they don't "affect" each other.

A really stupid test question, imo.


When another independent variable such as temperature is applied, vapor pressure would increase due to weakening of the intermolecular forces; surface tension would decrease thus allowing more molecules to escape and so the solubility would decrease. However, the mass transfer rate would increase at a fixed dissolved gas concentration. The temperature imparts kinetic energy to the liquid so the molecules are more agitated. These are the effects of temperature on both parameters. I agree with the premise that vapor pressure and surface tension do not affect each other.


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