Soaps have fatty acids with sodium atoms whereas detergents have sulfate groups, and both groups show different characteristics during the following chemical processes: different nature and level of hydrophilic interactions with R–SO3Na and R–COONa; and different steric effects caused by R–SO3Na and R–COONa. The detergents work effectively with pure water because the calcium (Ca2+) and magnesium cations that are present in hard water consume at least two times the normal amount of detergent. Soap solutions with Ca2+ form a soap scum as a white precipitate in place of forming micelles, which trap dust particles. Hardness is the soap-consuming capacity of a water sample through the precipitation of its alkyl chain. The precipitation prevents lathering of the soap as no micelle formation occurs. A detergent is a laundry or dish washing agent contrary to hand soap or other cleaning agents.