Soaps

Question 1

Formation of soaps

Answer 1

When fats are heated with an alkali - sodium hydroxide- they are hydrolysed.
Glycerol and a salt is produced.
The salt is soap

Question 2

How many molecules are produced from each molecule of fat/oil hydrolysed

Answer 2

3

Question 3

Structure of soap

Answer 3

They have a non-polar hydrocarbon tail that is hydrophobic

They have a negatively charged (COO-) polar, ionic head whip is therefore hydrophylic carboxylate head.

Question 4

How do soaps work

Answer 4

First mention structure of soap.
Hydrophobic tail will burrow into droplet of grease or oil due to both being non-polar so London dispersion forces will act between them so the tail is soluble in the grease.
Hydrophylic head are left to face surrounding water.
There is a formation of a ball like structure of the oil or grease called a micelle, these are suspended in the water to be washed away.

Question 5

How is the ball of fats/grease held together suspended in the water?

Answer 5

Once soap is mixed with grease or dirt then those substances will be broken up and held in suspension in the water due to the repulsion of the negatively charged ionic heads repelling one another - this is known as an emulsion

Question 6

What to remember for diagram of soap acting

Answer 6

Tails must be fully inside droplet and head must be on the outside

Question 7

Hard water

Answer 7

Water that has magnesium and calcium ions present

Question 8

Problems with soap

Answer 8

When hard water is present they will often fall a scum since the ions in the water will react with the head of the soap.
Soap is not very soluble in water so it only works well in hot water