Fats And Oils Flashcards
(18 cards)
Whydo oils have lower melting points compared to fats of similar molecular mass?
Their “degree of unsaturation” is higher, they contain more c=c
Which has a lower melting point, lard or olive oil?
Olive oil
What is the standard test for unsaturation?
Bromine solution decolorisation
What happens when oil is shaken with bromine solution?
The bromine solution becomes rapidly decolourised
What happens when fats found in a saturated organic solvent are treated this way?
Decolourisation is not so rapid
What is different about the structures of oils and of fats?
Oils have c=c which create a less compact structure that does not fit closely together.
Fats have few c=c which enable them to pack closely together.
Why does the difference in structure of fats and oils result in the difference in melting points?
The van der waals forces present in oils are weaker then those in fats since the molecules are not packed as closely together resulting in it being easier to break them.
What is process “hardening” ?
The conversion of soft liquid oils into harder solid fats
What kind of reaction is occurring during hardening?
Hydrogenation or addition
Give an example of a product made by hardening?
Margarine, from oils such as corn oil or soya bean oil
Describe the process of hardening?
Oil is heated with hydrogen in the presence of a nickel catalyst, hydrogen molecules add across the c=c, the unsaturation is partially removed converting liquid oil into hard fat.
What are fats and oils hydrolysed to?
Glycerol and fatty acids
What is formed for every mole of fat or oil that is hydrolysed?
One mole of glycerol and three moles of fatty acids are formed
What type of reaction forms the basis for soap making?
Hydrolysis
Describe the manufacture of soaps?
Fats of oils are boiled with sodium or potassium hydroxide solution. The alkali catalyses the hydrolysis reaction and then neutralises the fatty acids produced to form their sodium or potassium salts
What are soaps?
The sodium or potassium salts of fatty acids and a produces by the hydrolysis of fats and oils
Soaps are soluble so how are they extracted from the hydrolysis mixture?
The addition of a large excess of sodium chloride where the salt is then filtered of
Why are soaps useful for cleaning?
The covalent ‘tail’ bonds to the greasy material on fabric or skin, the ionic head is attracted to the polar covalent water molecules. An emulsion of globules of grease forms in the water
