Question #66e91

1 Answer
Jan 15, 2018




Surfactants are compounds that "lower the surface tension (or interfacial tension) between two liquids, between a gas and a liquid, or between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants." (Wikipedia)

You can explain the mechanism of soap using the principle of like dissolve like. For example, ethanol (#C_2H_5OH#) and petroleum ether, which is also not very polar, shows a miscibility- liquids' ability to mix with each other- higher than that of water.

Surfactant molecules in soap are usually amphiphile, meaning that they exhibit both polar and nonpolar characteristics. They help to break up chunks of insoluble materials which would otherwise be insoluble in water.

For example, Sodium lauryl sulfate (#NaC_12H_25SO_4#) acts as a common surfactant in detergent soap.
Dodecylsulfate, Wikimedia Commons

A #NaC_12H_25SO_4# molecule comes with two ends: a polar one that mixes well with water, comprised of a sulfate group (colored in red and yellow;) and a nonpolar one made up of a twelve-carbon chain (the greyish part) that dissolves many of the nonpolar substances. It helps removes fatty acids like vegetable oil and margarine in kitchens thanks to its amphiphilic nature.

Wikipedia contributors. "Surfactant." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 29 Dec. 2017. Web. 15 Jan. 2018.

Wikipedia contributors. "Petroleum ether." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 1 Aug. 2017. Web. 15 Jan. 2018.

Woodford, Chris. "How Do Detergents And Soaps Work?." Explain That Stuff, 2017,