The Two-Faced Detergent :: informative essay

Whether soil particles are attached to carpet fibers, wood floors or restroom sinks, they need to be removed. But how is this done? Most of us wipe or scrub a dirty surface with soap and water without a second thought about how they actually work to remove soil. The process of removing dirt begins at the molecular level. In order to understand how soap works, we must first acknowledge what soap actually does. By definition, soap is a mixture of sodium or potassium salts and long chain organic acids. One example of such a soap is Sodium stearate, NaCH3(CH2)16CO2. As you can see, a soap molecule is long. It has a carboxylate group called the head group which is polar and hydrophilic, or water attracting. The tail end is a fatty acid, which is non-polar and hydrophobic, or water repelling. In this way, soap is unique. One end attracts water while the other end pushes it away. Initially soaps where made by heating sodium hydroxide with beef fat. Beef fat contains an ester formed between glycerol and stearic acid. The ester is then attacked by the sodium hydroxide, which releases the stearic acid as sodium stearate, How does all this help soap clean things? Well soap dissolves in water. There is nothing special about this, since many substances have this property. Water is polar; the H2O molecules have an attraction for other polar substances such as soap, which is polar on the oxygen end of the molecule. When soap is added to water its head group, which is hydrophilic, is attracted to the water. Oil and grease etc. is non-polar, so only non-polar substances will dissolve in it. Therefore, oil and water do not mix. This is why Oil does not dissolve when you run water over it. How does the oil wash off your hands if the water isn ¡Ã‚ ¦t soluble with the oil? This is where soap comes in. While soaps head is attracted to water its tail is attracted to non-polar substances such as oil. When oil and grease etc. mix with oil it creates a slightly polar substance because of the head group. This makes the oil soluble with water allowing you to wash off your hands with water and rinse the grease off. Most detergents sold in stores today are more complicated then just a mixture of sodium or potassium salts and long chain organic acids.