How does soap work

A.� You probably don't think about it when you wash your hands or clothes, but the cleaning process actually occurs at the molecular level. Soap works by interfering with the bonds that dirt and the surface it clings to form.

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Q.� Is water important when using soap

A.� Yes. When dirt comes into contact with a surface your clothes or skin it is often because the particle of dirt and the surface molecules are attracted to each other by their opposite electrical charges. Dirt particle molecules may have a negative charge and the surface molecules may have a positive charge, bonding them together.

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When water is added into the equation things change: the water molecules form electrical double layers between the dirt particle and surface molecules. As the water molecules join with the molecules of the surface and the particles of dirt different molecular structures are formed. Whereas before the dirt and surface were attracted to each other, they now have similar electrical charges and so repel each other.

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In addition, if the surface is fibrous, like clothing, contact with water causes it to swell and so creates a physical distance between the surface and the dirt.

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Q.� Is water alone a sufficient cleaning agent then

A.� No. Because a surface or dirt can repel water, so the addition of a surfactant (detergent) is necessary.

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When a detergent is added into the equation its molecules stick to those of the dirt and surface, creating a new molecular bond that replaces the original bonds, so that now its the detergent that bonds to the dirt and to the surface. This new bonding by the soap separates the dirt from the surface, water is able to wash it away, leaving you, or your clothes, clean again.

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Do you want to know how a cosmetic works Read all about how antiperspirants work here or ask a new question here.

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by Lisa Cardy