12. Soaps, Detergents & Emulsions Flashcards
What 2 reactions occur in the making of soaps?
Hydrolysis and neutralisation
Describe the process of making a soap
1) fat is hydrolysed to form glycerol and 3 fatty acids
2) the fatty acid is then neutralised by an alkali and water is produced. The salt formed is soap
3) OH comes from alkali, H comes from fatty acid (Carboxyl group)
Name the two types of alkalis used in the process of making a soap
Sodium hydroxide
Potassium hydroxide
How do soaps work?
- soaps have a polar head and a non polar tail
- the polar head can dissolve in water and the non polar tail can dissolve in oils and grease
- The soap surrounds the oil or grease and the polar head hydrogen bonds to water so dissolves, keeping the droplet of grease in suspension
What is “hard water”?
Water containing Ca2+(aq) and Mg2+ (aq) ions
Why can’t soaps be used with hard water?
An insoluble “scum” forms due to Ca2+ and Mg2+ ions in hard water
What is a “soapless detergent” ?
A particle that contains a non-polar tail but a different ionic head from soap. They do not form scum with hard water
What are some problems with detergents?
Can irritate skin
Take longer to decompose than soaps
What are emulsions and name an emulsion you would find in real life
An emulsion is a mixture of two or more immiscible liquids (e.g water & oil), where the droplet of one liquid is held in suspension in another liquid by an emulsifier
Examples:
- mayonaise
- milk
- ice cream
Why are emulsifiers used?
Used to hold two immiscible liquids together
Why are emulsifiers used in industry?
- Help food look appealing
- Help to maintain quality of food
How are emulsifiers made?
Reacting edible oils with glycerol
How do emulsifiers work?
- Emulsifiers have a polar head and a non polar tail
- The polar head can dissolve in water-soluble compounds and the non polar tail can dissolve in the oil soluble compounds
- It surrounds the droplet keeping it in suspension
What is added to edible oils to make emulsifiers?
Gylcerol
