A detergent is substances which has a power to cleanse. This description applies to soap, as well as to soap, as well as to soapless shampoos and washing powders. A detergent usually has surface activating properties, which means that it is able to reduce the surface tension of water.
In the process of cleaning the detergent acts as a bridge between the solid matter and the water. Soap molecules are shaped like tadpoles. The head is soluble, but the rod-like body is composed of an insoluble fatty substance. When mixed with water part of the soap tries to get away and the rest stays, thus breaking down the water’s surface tension. There is not sufficient room for all the soap molecules on the surface of the water. So they form bundles with the water-resisting rods on the inside. The dirt attracts the fatty part of the soap molecules which lift and surround it, while the soluble part of the molecules lifts and rinses the dirt away.
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