How does soap work?
Is antibacterial soap any better than regular soap? It seems like everything is “antibacterial” these days. About 75 percent of liquid soaps currently on shelves in American grocery stores display that word on their labels, and we are constantly adding new antibacterial products to our cleansing arsenals. So are we cleaner now than ever before? Some experts say no. First let’s take a look at how soap works on a chemical level. To make soap, you need to combine an acid and a base (or alkali). The acid is fat (fatty acids and triglycerides), and the base is sodium hydroxide (NaOH). The mixture causes the fatty acids to separate from the triglycerides and fuse with the hydroxide ions, forming a salt that we call “soap.” Soap has two main functions: 1. Decrease water’s surface tension 2. Bind to dirt, oil and bacteria It can do these things because one part of the soap molecule is hydrophilic (water-binding) and the other is hydrophobic (water-repellent). The hydrophilic part allows the hy
Nearly all compounds fall into one of two categories: hydrophilic (‘water-loving’) and hydrophobic (‘water-hating’). Water and anything that will mix with water are hydrophilic. Oil and anything that will mix with oil are hydrophobic. When water and oil are mixed they separate. Hydrophilic and hydrophobic compounds just don’t mix. The cleansing action of soap is determined by its polar and non-polar structures in conjunction with an application of solubility principles. The long hydrocarbon chain is non-polar and hydrophobic (repelled by water). The “salt” end of the soap molecule is ionic and hydrophilic (water soluble). When grease or oil (non-polar hydrocarbons) are mixed with a soap- water solution, the soap molecules work as a bridge between polar water molecules and non-polar oil molecules. Since soap molecules have both properties of non-polar and polar molecules the soap can act as an emulsifier. An emulsifier is capable of dispersing one liquid into another immiscible liquid.
Soap was first made from boiling beef fat (called tallow) with ashes. That’s right like ashes you get from burning wood. The mixture made the molecules in soap have a unique property. The longest part of a soap molecule called the tail repels water (It acts like it hates water and this is called hydrophobic). At the same time a special part at the head of the molecules attracts water. (It acts like it loves water and this is called hydrophilic.) The reason soap molecules are good for cleaning is that oily things like to stick together…just like oil molecules like to stick together in a bottle of salad dressing. Why do we need to use soap? Most soils we come in contact with are water soluble which means water and the motion of the washing machine are enough to clean clothes. If clothes are extra dirty, the dirt may settle back on the clothes instead of going down the drain. Detergents (or soaps) are needed because they use chemicals that keep the dirt floating in the water so that it
