Nature's Chemistry: Soaps, Detergents and Emulsions

Question 1

What are soaps?

Answer 1

Fatty acid salts formed from the alkaline hydrolysis of fats or oils

Question 2

Soap molecules contain what?

Answer 2

A non-polar tail and a polar head

Question 3

How can soaps dissolve greasy/oily stains?

Answer 3

As the non-polar tail will dissolve in the grease, coating the outside of the stain with repulsive negative charges from the polar heads. This causes the stain to break down into water-soluble globules which can be washed down the sink.

Question 4

What are detergents?

Answer 4

Soap-like molecules which will not form scummy precipitates with hard water as they have different polar heads from soaps

Question 5

What are emulsifiers used to do?

Answer 5

Keep water-soluble and oil-soluble compounds together. They are widely used in the food industry and can be recognised as they have a non-polar part and a polar part.

Question 6

What is an emulsifier?

Answer 6

An emulsifier is a soap-like molecule which prevents an emulsion separating out into separate liquids. Emulsifers have one or two fatty acid molecules added to a glycerol molecule.

Question 7

What is an emulsion?

Answer 7

An emulsion contains small droplets of one liquid dispersed in another liquid, e.g. oil and water