KA4- Soaps, Detergents And Emulsion

Question 1

When fats and oils hydrolyse

Answer 1

Produce glycerol and carboxylic acids known as fatty acids
If carried out using an alkali, fatty acids immediately react to from salts which are what we commonly refer to as soaps

Question 2

Soap

Answer 2

Fatty acid salts formed from the alkaline hydrolysis of fats or oils
Can dissolve greasy/oily stains as the non-pola tail will dissolve in the grease, coating the outside of the stain with repulsive negative charges from the polar heads
Causing the stain to break down into water-soluble globules
fats and oils are non-polar compounds so they will not readily dissolve in water

Question 3

Soap molecules

Answer 3

Contain long, non-polar hydrocarbon chains since the carboxylic acids found in fats and oils have long hydrocarbon chains and a soap is the salt of a Carboxylic acid

Question 4

Soap properties

Answer 4

Contain a carboxylate head formed from the reaction of the carboxyl group with the base
Have a polar head and a non-polar tail
An ionic head which is water soluble
A hydrocarbon tail which is soluble in oil and grease

Question 5

Hydrocarbon tail (of soap)

Answer 5

Can bond easily to greasy stains on clothes or skin
Doesn’t dissolve in water- hydrophobic

Question 6

Ionic head

Answer 6

Does dissolve in water- hydrophilic

Question 7

Soap dissolving in grease

Answer 7

Causes it to be covered in negative charge- resulting in the grease breaking up into globules which are attracted to water allowing them to be washed away when water is added

Question 8

Detergents

Answer 8

Compounds with a soap-like structure which allows them to remove greasy stains
Non-polar tail which is oil soluble
Polar head which is water soluble
Will not from scummy precipitates with hard water as they have different polar heads from soaps

Question 9

Difference between detergents and soaps

Answer 9

The head- detergents will always be soluble in water
Detergents do not have a carboxylate head
Detergents will not for precipitates in hard-water areas
Detergents do not form precipitates with calcium or magnesium ions as they do no contain the carboxylate ions so are very useful in hard-water mass areas as an alternative to soap

Question 10

Emulsion

Answer 10

A liquid which contains small droplets of another liquid such as soapy grease particles mixed in water
Grease and water usually separate into 2 layer but soap acts as emulsifier, bringing the 2 substances together
Common in food

Question 11

Emulsifiers

Answer 11

Used to keep water-soluble and oil-soluble compounds together
Widely used in the food industry
Can be recognised as they have a non-polar and polar part