soaps detergents and emulsions Flashcards
how are soaps produced ?
the alkaline hydrolysis (heating under reflux w an alkali) of edible fats/oils using sodium or potassium hydroxide.
what does the alkaline hydrolysis of soap produce?
one glycerol molecule and 3 fatty acids, which are neutralised by the alkali, forming water soluable, ionic salts (or, soap!)
what is the structure of soap?
long non polar tails (thus, hydrophobic) and ionic heads (hydrophilic)
how does soap clean?
- the non polar hydrophobic tail dissolves in the non polar grease of oil. the ionic heads remain on the surface of the grease in contact with the water
- agitating the water breaks the grease loose forming globules covered in the ionic (negative) heads.
- because they are negative, the ionic heads repel each other if they come close to the other oil globules meaning they cannot re join to form a large blob again.
what is an emulsion?
a mixture of two or more immiscible liquids.
what is soap a type of ?
emulsifier
what is hard water?
water containing high levels of dissolved metal ions.
what happens when hard water reacts with soap?
scum, an insoluable precipitate, is formed.
what is used instead of soap in areas with hard water?
soapless detergents
describe the structure of soapless detergents
they still have an ionic hydrophilic head, and a long non polar hydrophobic tail but are formed from hydrocarbon molecules from crude oil.
how are emulsifiers used ?
in food to prevent the oil and water within it from separating (e.g, mayonnaise, bread, biscuits, ice cream.)
how are emulsifiers used in food formed and what is the products structure like?
by reacting edible oils with glycerol. in the molecule 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.
