Page 36 - Curriculum Visions Dynamic Book

Soap
The reaction of sodium hydroxide with fat can be used to make soap. Soap is a waxy solid used in cleaning. It is different from a detergent, whose chemical action is based on petroleum products.
Soap-making is one of the most ancient chemical reactions, used for at least two thousand years. It was used not just for cleaning, but also for keeping skin healthy. It was noticed that when people washed in soap, they were much less prone to skin diseases.
Saponification
Soap can be made easily in the laboratory. In the flask shown below oil has been gently added to a volume of sodium hydroxide solution in water. It forms a yellow layer on the top of the hydroxide.
The flask and its contents are boiled with a condenser over the top of the flask to make sure that nothing evaporates during the boiling process. After a while the whole of the liquid takes on an opaque appearance and bubbles begin to appear on the surface. This is liquid soap.
 This end of the sodium stearate molecule is repelled by water and molecules of the same type but is attracted to grease. The chemical formula for this molecule is C17H35CO2Na.
After boiling, the Oil solution becomes
Sodium hydroxide solution.
The round bottomed flask is heated and the contents boil.
Also...
When soap is used in hard-water areas the water often develops a scum that forms a deposit on bath tubs and on clothes. This scum is formed because the soap molecule is attracted to the calcium and magnesium salts in hard water and it combines with these minerals to form a white precipitate rather than dissolving grease away.
Detergents are used for washing to prevent this problem; however, detergents are too harsh for use in washing skin. The scum can be counteracted by using a water softening agent (such as bath salts, sodium carbonate) in the bath or in the soap.
opaque. Soap has been produced.
Hydrogen
Oxygen
Carbon
Sodium
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