Surfactants (1 Viewer)

[Run hard@thehsc]

How can I explain that soaps/detergents are surfactants? Thanks!

 

[wizzkids]

Surfactant is short for "surface active agent". There are two ways to answer your question. We can cite experimental evidence, or we can give the theory. I will give some evidence. Soaps and detergents concentrate at interfaces as a mono-molecular layer. For example, their presence in the solvent water will alter its interfacial properties. Normal water has strong hydrogen bonding, and therefore a strong surface tension. However, in the presence of soaps or detergent, the surface tension is much reduced. The water will form bubbles easily, and the bubbles are stabilised by the mono-molecular layer, so soaps and detergents will make a stable foam. Pure water does not do this. The mono-molecular layer also stabilises the dispersion of fine oil droplets in water due to the formation of a micelle. Pure water does not do this.