Unit 2: Soaps, Detergents & Emulisions

Question 1

How are soaps produced?

Answer 1

Soaps are produced by the alkaline hydrolysis of edible fats and edible oils.
Hydrolysis produces 3 fatty acid moleucles and one glycerol molecule.
Fatty acids produced are neutralised by alkali forming water-soluable ionic salts called soaps.

Question 2

What are Soaps used for?

Answer 2

Soaps are used to remove non polar substances such as oil and grease. Oils and Grease do not mix with water.

Question 3

What is the Non-Polar tail called in a soap molecues?

Answer 3

Hydrphobic Non-Polar Tail.

Question 4

What is the Polar head called in a soap molecule

Answer 4

Hydrophilic Polar Head.

Question 5

What happens to a soap molecule when mixed with oil or grease.

Answer 5

• Hydrophobic tails dissolves in the droplets of oil/grease
• Negativly-charged polar head is hydrophilic so head faces out into surrounding water
• Agitation causes ball like structures to form
• Non-polar substance such as oil/grease are held inside the ball and suspended in the water
• Repulsion prevents the oil droplets re-joining and helps disperese the oil

Question 6

What is Hard Water?

Answer 6

Hard water is the term used to describe water containing high levels of dissolved metal ions.

Question 7

What happens when soap is used in Hard Water?

Answer 7

When soap is used in hard water, an insoluable precipate forms which is know as scum.

Question 8

What are soapless detergents?

Answer 8

Soapless detergents are substances with non-polar hydrophobic tails and ionic hydophilic heads. Soapless detergents do not form scum with hard water. Soapless detergents remove oil/grease the same way as soaps do.

Question 9

What can emulsifies be used for?

Answer 9

An emulsifier can be used to prevent non-polar and polar liquids separating into layers.

Question 10

What is an emulsion?

Answer 10

Emulsions are formed when tiny droplets of one liquid are suspended within another liquid. (A mixture of oil and water is a good example of an emulsion)

Question 11

How can emulsifiers for food be made?

Answer 11

Emulsifiers for food can be made by reacting edible oils with glycerol.
Molecules formed in this reaction have one or two fatty acids linked to each glycerol backbone.
Hydroxyl -OH group(s) in the emulsifier formed are hydrophilic
The fatty acid(s) attached from the glycerol back bone are hydrophobic
Hydrophobic fatty acid chains dissolve in oil while the hydrophilic hydroxyl -OH groups dissolve in water
Together a stable emulsion is formed