UNIT 2 : Soaps, Detergents and Emulsions

Question 1

How are soaps made?

Answer 1

We add Sodium Hydroxide to a fatty acid and are left with water and a fatty acid which has an Na+O- group (soap) instead of an OH group

Question 2

What do we add to the reaction to make a soap?

Answer 2

Sodium Chloride

Question 3

Why do we add Sodium Chloride to the reaction to make a soap?

Answer 3

To ensure that all of the unstable fatty acid molecules have a Na+O- group bonded to them

Question 4

What happens to the chloride ions once all of the soap molecules are created?

Answer 4

They just float around in the water

Question 5

What ion, other than Na+, is used in soaps often?

Answer 5

K+ (from Potassium Hydroxide)

Question 6

What are soaps in simple terms?

Answer 6

Salts of fatty acids

Question 7

What is meant by the term hydrophyillic?

Answer 7

A substance/molecule which is attracted to water and it dissolves in polar solvents

Question 8

What is meant by the term hydrophobic?

Answer 8

A substance/molecule which repels water

Question 9

What part of the soap molecule is hydrophyllic?

Answer 9

The -COO group

Question 10

What part of the soap molecule is hydrophobic?

Answer 10

The long carbon chain (“tail”)

Question 11

How does soap clean things?

Answer 11

When in water, the soap molecule’s “tail” goes into the grease molecule, while the “head” and positive ion stays outwith the grease. This then lifts off of the surface in small ball like molecules and the ion detaches from them

Question 12

What are the small ball like molecules called?

Answer 12

Micelles

Question 13

What causes the small ball like molecules to suspend in water?

Answer 13

The repulsion of the negatively charged heads

Question 14

What is an emulsion?

Answer 14

When two liquids are suspended in each other by the repulsion of their negatively charged heads

Question 15

What are detergents made of?

Answer 15

Crude oil

Question 16

When would we use a detergent instead of a soap?

Answer 16

For tougher stains

Question 17

What do detergents work in a similar way to?

Answer 17

Soaps

Question 18

What is the difference between soaps and detergents?

Answer 18

Detergents don’t cause an insoluble precipitate (scum) in the same way a soap would

Question 19

What is similar between soaps and detergents?

Answer 19

They both have hydrophobic and hydrophilic parts

Question 20

What are biological detergents (enzyme detergents) used for?

Answer 20

Blood or sweat etc

Question 21

How are biological detergents made?

Answer 21

Naturally

Question 22

Where and why are emulsifiers used?

Answer 22

In food to separate oil and water and thus, prevent food spoilage

Question 23

How are emulsifiers for use in food consumption commonly made?

Answer 23

By reacting edible oils with glycerol to form molecules in which there are either on or two fatty acid groups compared to the usual three

Question 24

In emulsifiers, what part of the molecule is hydrophobic and what part is hydrophylic?

Answer 24

The OH groups are hydrophilic, and the fatty acid chains are hydrophobic