Detergent, Mayonnaise, Emulsions and Emulsifiers
Washing the dishes
Have you ever tried to wash up oily plates in hot water?
It is not easy!
This is because oil and water don’t mix.
If washing up liquid is added the plates are easily cleaned.
Oil does not attract water. Oil repels water.
A detergent in washing-up liquid provides ‘hooks’ between oil and water.
The oil is ‘hooked’ onto the water and pulled off a dirty plate.
This is an example of an emulsion.
A detergent is an emulsifier.
Examples of emulsions
· If oil leaks into the sea it can harm sea birds and other sea life.
To disperse an oil slick, detergent is sprayed from light aircraft over the area of the slick.
The detergent ‘hooks’ the oil onto the water and it is then much easier to clean up. The detergent acts as an emulsifier.
· Some paints are emulsions.
· Milk is an emulsion.
· Mayonnaise is an emulsion of oil and vinegar with egg. Egg is the emulsifier.
How does a detergent work?
Detergents are long molecules made up of two parts, a head and a tail. The tail is a ‘fat-loving’ part and the head is a ‘water loving’ part.
More on mayonnaise
Mayonnaise is a food made using egg as an emulsifier.
The egg yolk binds the oil and vinegar together to make a smooth substance.
The mayonnaise does not separate because the egg yolk contains a molecule that has two parts.
One part is a water-loving part that attracts vinegar to it. This is called the hydrophilic head.
The other part is a water-hating part that attracts oil to it. This is called the hydrophobic tail.
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