unit 2 KA4 - soaps, detergents and emulsions Flashcards
how are soaps produced - explain in detail
by the alkaline hydrolysis of edible fats and edible oils. hydrolysis produces three fatty acid molecules and one glycerol molecule. the fatty acid molecules are neutralised by the alkali, forming water-soluble, ionic salts called soaps
what is the use of soap
to remove non-polar subtances such as oil and grease
what is the structure of soap
each molecule consists of a long non-polar, covalent, hydrocarbon, hydrophobic and oil soluble tail and a polar, ionic, hydrophilic, water soluble head, where the charge is.
how does soap work according to the course specifications
the hydrophobic tails on the soap dissolve in the oil or grease, and the negatively charfed hydrophilic heads remain pointing up in the surrounding water. agitation causes ball-like structures to form, and the negatively charged ball like structures repel each other and the oil or grease is kept suspending in water
describe the steps to how soap works
the tails burrow into the greasy, non-polar molecule. in the same way, the heads are attracted to the polar water. the head groups all point up into the water at the top of the grease stain.
the attraction of the head group to the surrounding water is so strong that it causes a mechanical lift of the grease molecule away from the material on which it was deposited.
the tails are anchored in to the grease due to the non-polar-to-non-polar attraction. the combined efforts allow for the removal of the grease stain.
what is hard water
a term used to describe water containing high levels of dissolved metal ions. when soap is used in hard water, scum, an insoluble precipitate, is formed
what are soapless detergents
substances detergents are substances with non-polar hydrophobic tails and ionic hydrophilic heads. these remove oil and grease in the same way as soap. soapless detergents do not form scum with hard water.
what is an emulsifier
these are subtances used to prevent non-polar and polar liquids separating into layers.
what is an emulsion
emulsions are substances that contain small droplets of one liquid dispersed in another liquid
how can emulsifiers be made, and how do they work?
emulsifiers can be made by reacting edible oils with glycerol. in the molecules formed, only one or two fatty acid groups are linked to each glycerol backbone. the hydroxyl groups present in the emulsifier are hydrophilic whilst the fatty acid chains are hydrophobic. the hydrophobic fatty acid chains dissolve in oil whilst the hydrophilic hydroxyl groups dissolve in water, forming a stable emulsion.
