Unit 2-Soaps, Detergents and Emulsions

Question 1

How are soaps made?

Answer 1

Soaps are produced from the alkaline hydrolysis of fats and oils (Triglycerides)

Question 2

What else is made in the following reaction? Fat or oil + Sodium Hydroxide –> Soap + ????

Answer 2

Glycerol

Question 3

Describe the structure of a soap molecule.

Answer 3

Long non-polar covalent hydrocarbon ‘tail’ and a polar, ionic ‘head’.

Question 4

What word can be used to describe the tail of a soap molecule which is repelled by water?

Answer 4

Hydrophobic

Question 5

What word can be used to describe the polar ionic head of a soap molecule which can dissolve in water?

Answer 5

Hydrophilic

Question 6

How does the structure of soaps allow it to clean?

Answer 6

During cleaning using soaps the hydrophobic tails dissolve in a droplet of oil or grease, whilst the hydrophilic heads face out into the surrounding water

Question 7

What word is used to describe small grease droplets suspended in water?

Answer 7

Emulsion (micelle)

Question 8

Detergents are particularly useful in hard water areas because they do not form scum.

How does a detergent clean?

Answer 8

Tails would dissolve into the fat-soluble dirt.

Question 9

Why are emulsifiers added to foods?

Answer 9

To prevent the oil and water from separating and stop the food from spoiling.

Question 10

Identify the hydrophobic and hydrophilic parts of these emulsifiers.

Answer 10

Hydroxyl groups are hydrophilic, whilst fatty acid chains are hydrophobic.