# How to reduce surface tension of water?

I'm working on a project and I need to reduce the surface tension of water. I want you to tell me a way in order to reduce surface tension of water except changing the temperature.

• The first idea that comes to mind is putting some drops of soap or detergent in the water. Commented Nov 27, 2015 at 7:26
• yes find something that is able to interfere with the intermolecular attraction of the water molecules. Detergent works well for this. Introducing another pollutant like salt may work as well. Commented Nov 27, 2015 at 7:42
• Any soap, detergent, surfactant or emulsifier will achieve this. Commented May 15, 2016 at 16:47

Reduction of surface tension of water can be done in several ways. A few of them are as follows:

Surfactants are compounds that lower the surface tension of a liquid like water, the interfacial tension between two liquids, or that between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants.

1. Surface tension can change with the change with medium that is just above the liquid. For instance, If the medium is air the surface tension of water is $72 \times 10^{-3}\,\mathrm{N/m}$, but if the medium is vapour that will be $70 \times 10^{-3}\,\mathrm{N/m}$
2. If there is any oil or oily compounds on the free surface of the water, then surface tension will be reduced.
3. If you mix something to the water, then the surface tension will be changed.
4. If you electrify the water then surface tension will be reduced.

Existing surfactants can lower it either as a monomolecular layer on water surface (Langmuir monolayers) or by forming microemulsions. In the former, the bulk water composition is unchanged but the surface tension can be reduced from $72\,\mathrm{mN/m}$ to only about $20\,\mathrm{mN/m}$. The microemulsion can make the interfacial tension go to $1\,\mathrm{\mu N/m}$ but changes the water composition. We have shown, through measurement of capillary wave amplitudes using diffuse scattering of X-rays, that a bi-molecular layer of a three-tailed amphiphile, preformed ferric stearate (FeSt), on water surface , lowers the surface tension to about $1\,\mathrm{mN/m}$.