Show a chemical structure for soap.
What is unique about the polarity (charge characteristics) of soap?
My-cell; charged characteristics which help trap fats in the center of the molecules. The fatty acid within the soap is turned into a salt because of the presence of a basic solution of the NaOH. In the carboxyl group, one oxygen (red) now has a negative charge that attracts the positive sodium ion. Which again describes how the soap helps trap oils/fats.
How does soap work?
“When you mix soap into the water the soap molecules arrange themselves into tiny clusters (called 'micelles'). The water-loving (hydrophilic) part of the soap molecules points outwards, forming the outer surface of the micelle. The oil-loving (hydrophobic) parts group together on the inside, where they don't come into contact with the water at all. Micelles can trap fats in the center.” http://www.edinformatics.com/interactive_molecules/soap.htm
“It is difficult to wash an oil spot out of clothing with plain water, because oil is a hydrocarbon that does not dissolve in water. Oil and water actually repel one another, so that oil adheres even more strongly to clothing in the presence of water. The addition of soap or detergent to water changes the situation; soapy water can dissolve oil from clothing and rinse it away. It is the long hydrocarbon chains of the stearate anions that dissolve the oils and greases. If water containing dissolved soap is mixed with oil, the hydrocarbon chains strongly attract the oil, while the ionic ends keep the soap dissolved into water. The oil spot is broken up into small droplets and dispersed into the water. The "tails" of many soap anions are needed to remove each oil droplet.” http://www.brookscole.com/chemistry_d/templates/student_resources/0030012910_kotz/appchem/ch11/carbon10.html
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