Fats, oils and soaps Flashcards
What is glycerol (3 points)
-Trihydric alcohol
-3 OH
propoan-1,2,3,-triol
Define how the triglyceride molecule is formed
Where glycerol undergoes a condensation reaction with 3 fatty acid molecules
Explain why fats are solids at room temp
-The fatty acid chains that make up fats are mostly saturated.
-This gives a rise to molecules with carbon chains and so can pack closely with other fat molecules
-This allows many LDF to be set up
Explain why oils are liquids at room temp
-The fatty acid chains that make up oils have 1 or more carbon to carbon double bond.
-The double bond distorts the long fatty acid chains and so the molecules cannot pack as closely together
-This gives a rise to weaker LDF and so less energy is needed to break the molecules
Test for fats or oils
Fat decolourises slowly in bromine water
Oil decolourises immediately in bromine water
Define hydrogenation
An addition reaction of hydrogen across a carbon to carbon double bond.
Catalyst and name for process in hydrogenation
Nickel catalyst - hardening
Why we need fats and oils in diet
- Energy
- Animal fats contain important fat soluble vitamins such as D and E
Why are fats and oils good solvents
Nonpolar nature means they will dissolve nonpolar vitamins such as A,D,E,K
What can be used when preparing an ester using a water bath and test tube
Wet paper towel condenser at top of test tube
How is soap produced
Alkaline hydrolysis of fats and oils (saponification)
Most common type of soap
Sodium stearate
How does the cleansing action work
-Hydrocarbon side is pure and so hydrophobic
-Negative side is polar and so hydrophilic
Word to describe detergents
Synthetic
Define hard water
Water containing Ca and Mg ions
What can the ions do in hard water
Form unwanted salts with soaps
Solutions to hard water salts
Use soapless detergents
How are detergents different and similar to soaps
Have a soap like structure due to hydrocarbon tail and ionic head yet the molecules dont form precipitate
Explain cleansing action
-The covalent non-polar, hydrophobic tails will dissolve in grease, oil and other non-polar solvents.
-The ionic, hydrophilic heads end will dissolve in water and aqueous solutions.
3 mark explaining why the cleansing action is effective
-The negative ionic heads covering the surface of a grease layer and with agitation, the grease is broken up into small ball-like structures.
-The negative ball-like structures (micelles) repel each other and the grease is dispersed through the water.
-The grease has been emulsified by the soap and rinsing with clean water washes these grease and oil droplets away.
what is the process called when fats and oils break down
hydrolysis
define an emulsion
contains small droplets of one immiscible liquid dispersed in another
what does an emulsifier do
makes an emulsion more stable by holding the oil droplets in water for longer
2 examples emulsifiers in food
Mayonnaise
Lecithin is a natural emulsifier in egg yolk
how are synthetic emulsifiers for food made
by reacting edible oils with glycerol
why do detergents not react with Mg and Ca
contain a sulfanoate ion
why are certain emulsifiers good
polar and nonpolar ends of the molecule
define hardening
when hydrogenation occurs (addition of H) across a carbio to carbon double bond. a nickel catalyst is used
use for sodium salts of fatty acids
soaps
