soaps, detergents and emulsions 2.3 Flashcards
how are soaps formed
from the alkaline hydrolysis of fats and oils
when does the ester link in fats or oils breakup
when the ester is heated with sodium or potassium hydroxide
what does the hydrolysis of fats and oils produce
3 fatty acid molecules and 1 glycerol molecule
what happened in the alkaline hydrolysis reaction
the fatty acids are neutralised and the water soluble ionic salts called soaps are formed
soap ion structure
have long non polar tails, readily soluble in non polar compounds (hydrophobic) and ionic heads that are water soluble (hydrophilic)
how soap works
- the hydrophobic tail dissolves in the oil or grease
- the negatively charged hydrophilic heads remain in the surrounding water
- agitation causes ball like structures to form
- the negatively charged ball like structures repel each other and the oil or grease is kept suspended in the water
detergents
work in a similar way to soaps but are more useful in areas where the water is hard
what is hard water
water that contains high concentrations of dissolved metal ions
why is detergent preferred to soap in hard water
the soap and water form insoluble precipitates called scum and the detergents don’t form scum
emulsions
contain small droplets of one liquid dispersed in another example oil droplets when mixed with water
what do emulsifiers allow
for stable emulsions to form
how do emulsifiers work
they stop emulsion from separating out
how are emulsifiers for food made
by reacting edible oil with glycerol and 1 or 2 fatty acids bind to a glycerol forming ester links
why are emulsifiers added to foods
in order to stop oil and water from separating and the food spoiling quickly
emulsions structure
the remaining hydroxyl groups on the glycerol are polar and form the hydrophilic head and the long non polar carbon chain forms the hydrophobic tail
