Unit 2: Soaps

Question 1

How are soaps formed

Answer 1

Alkaline hydrolysis (breaking up) of fats and oils by sodium or potassium hydroxide by boiling under reflux conditions

Question 2

Step 1 of making soap

Answer 2

Hydrolysis produces three fatty acid molecules and one glycerol molecule

Question 3

Step 2 of making soap

Answer 3

Fatty acid molecules neutralised by the alkali, forming water soluble, ionic salts called soaps

Question 4

Why use soap

Answer 4

Water on non-polar substances like grease due to fats, do not dissolve in water. Water is polar, grease is non polar

Question 5

How soaps work step 1

Answer 5

Hydrophobic non-polar tail dissolves into droplets of oil and grease

Question 6

How soaps work step 2

Answer 6

Negative ionic hydrophilic heads remain in surrounding water

Question 7

How soaps work step

Answer 7

Agitation causes ball-like structures called micelles to form

Question 8

How soaps work step 3

Answer 8

Negatively-charged ball-like structures repel each other and oil or grease is kept suspended in water stopping the grease from forming back together

Question 9

Soapless detergents

Answer 9

When soap is used in hard water, charged calcium and magnesium ions present react with soap to form the insoluble substance scum.

Question 10

Soapless detergents

Answer 10

Non-polar hydrophobic and ionic hydrophilic heads, remove oil in the same way as soap