Soaps, Detergents and Emulsions Flashcards
What is formed when fats and oils are hydrolysed used an alkali?
Salts of the long-chain fatty acids are formed called soaps. Glycerol is also formed.
Describe the tail of a soap molecule.
The tail is a long covalent hydrocarbon meaning it is non-polar, and will therefore be insoluble in water - hydrophobic. It is, however, soluble in covalent substances like grease and oil.
What type of molecule is soap?
A salt
Describe the head of a soap molecule.
The head is ionic or negatively charged, making it hydrophilic.
What happens when soap is used in hard-water areas?
Insoluble salts (precipitate) form, known as scum. An example of this is calcium stearate.
What ions does hard water contain?
Calcium and magnesium ions; dissolved metal ions.
What cleaning product is used in hard-water areas instead of soap?
Detergent as it works in a similar way to soap, however, does not form insoluble salts - meaning it can lather.
Describe the structure of detergent.
The molecule is similar to soap in that it has a hydrophobic hydrocarbon tail and a hydrophilic ionic head.
How does soap work?
- Soap dissolves in water, forming soap ions.
- Tails of soap ions bury into grease leaving their heads in the water.
- Agitation begins to separate grease from the surface causing grease globules to form in the water.
- Micelles are prevented from recombining by negative charges on heads of soap ions in the water.
What is an emulsion?
A mixture of two or more liquids that are normally immiscible, due to polarity.
Contains small droplets of one liquid dispersed in another liquid.
What is an emulsifier?
They allow normally immiscible liquids to mix and stop them from separating.
What are emulsifiers in food?
Mixtures of fat/oil and water.
What are food examples of emulsions?
Milk and mayonnaise
What is the natural emulsifier in milk?
A protein called casein.
How can emulsifiers be made?
By reacting edible oils with glycerol.
What other molecule are emulsifiers like?
Soap - they also have a hydrophobic part and a hydrophilic part.
How does an emulsifier hold a mixture together?
The hydrophobic part dissolves in the fat/oil and the hydrophilic part dissolves in the water - holding the mixture together.
What are E numbers?
Food additives/emulsifiers
Describe these E numbers:
- E332
- E471
- Lecithin - found naturally in eggs. It is used as an emulsifier in mayonnaise, chocolate, margarine, and chewing gum.
- Mono- and di- glycerides - the most commonly used emulsifier in the food industry. Used in ice cream, bread, and sausages.
What’s another effect of emulsifiers on food products?
They can keep products fresher for longer - and in some cases help prevent mould.
How is soap produced?
By the alkaline hydrolysis of edible fats and edible oils.
What does the hydrolysis of edible fats and edible oils produce?
Three fatty acid molecules and one glycerol molecule.
From fatty acids, how is the soap then produced?
The molecules are neutralised by the alkali forming water-soluble ionic salts - called soaps.
What are soaps used for?
To remove non-polar substances such as oil and grease.
