Dirty cloths containing grease and oil stains are cleaned by addingdetergents to water. Stains are removed because detergentreduces drastically the surface tension between water and oil.Detergents are primarily surfactants that lower the surface tension ofwater, essentially making it 'wetter' so that it is less likely to stick toitself and more likely to interact with oil and grease. Like soaps,detergents have hydrophobic or water-hating molecular chainsand hydrophilic or water-loving components. The hydrophobichydrocarbons are repelled by water but are attracted to oil and grease. The hydrophilic end of the same molecule means that one end of the molecule will be attracted to water, while the other side isbinding to oil. With some agitation the stains are cleaned.