How Does Soap Work?

Soap is ubiquitous, a household staple near sinks and showers--indeed, everywhere. This ancient cleanser, beauty product and source of cheap childhood entertainment, is basic chemistry in action. Soap is more than just a cleaning agent composed of a salt and a fatty acid; it is a vital life-saving tool that prevents the spread of illness and disease. Soap is so important that the US Centers for Disease Control and Prevention state that washing hands with soap and water is one of the most important tools in preventing the spread of illness.

Soap is defined as an emulsifier--a compound able to dissolve a substance into another. Soap binds to other fats, oils and dirt, washing them away in water. Soap and water are indispensable in everyday life, carrying unwanted dirt, germs and debris away from us.

Soap's Structure Gives it Cleansing Power

All molecules can be classified by the types of chemical attractions they have. Polar molecules have unequally distributed electrons, resulting in a molecule that has a partial charge in one region. Polar molecules are typically hydrophilic (attracted to water), water soluble and polar. Non-polar molecules are often hydrophobic and lipophilic, or attracted to fat molecules.

Soap is composed of polar and non-polar ingredients therefore it can attract and dissolve both water and oil. The long non-polar portion of the soap dissolves other non-polar materials such as fats and oils. The polar portion is important because it provides solubility

The Process of Clean

When soap is dissolved the hydrophobic fatty acid chain is repelled by water and attracted to oils. The fatty acid portion of the soap dissolves any oils present and surrounds the oil in a circle of fatty acids. Because the soap is surrounded by water molecules the hydrophobic fatty acid chains quickly point in-ward toward the oil. In turn, the hydrophilic salt end turns outward towards the water and assists in keeping the particles of oil from re-dissolving in one another. With the oil now trapped and suspended in the fatty acid chains of the soap molecules it can be washed away and removed from the item being cleaned.

There are many characteristics of soap that may be altered such as lather, scent, color and solubility, but the fundamentals of the process remain constant. These fundamental cleaning properties make soap a popular and important tool for people worldwide.