Soaps and detergents Flashcards
What parts does a soap molecule have?
A polar/ionic (-) hydrophilic ‘head’ and a non-polar hydrophobic tail
What does the head interact with?
the polar water molecules
What does the tail interact with?
the grease molecules
In a soap molecule, what part is the soap?
the sodium salts of fatty acid
How are soaps produced?
By the alkaline hydrolysis of edible fats and edible oils.
The hydrolysis produces 3 fatty acid molecules and one glycerol molecule
The fatty acid molecules are neutralised by the alkali, forming the water-soluble, ionic salts called soaps
What are soaps used for?
To remove non-polar substances such as oil and grease
What causes a ball-like structure to form?
Agitation
The negatively charged ball-like structures repel each other and the oil or grease is kept suspended in the water
How do soaps work?
During cleaning, the hydrophobic tails dissolve in a droplet of oil or grease, whilst the hydrophilic heads face out into the surrounding water.
Agitation of the mixture results in a ball-like structure forming with the hydrophobic tails on the inside and the negative hydrophilic head on the outside.
Repulsion between these negative charges results in an emulsion being formed and the dirt released
What is hard water?
A term used to describe water containing high levels of dissolved metal ions
What happens when soap is used in hard water?
Scum, an insoluble precipitate, is formed
What are soapless detergents?
substances with non-polar hydrophobic tails and ionic hydrophilic heads. These remove oil and grease in the same way as soap
Do soapless detergents form scum with hard water?
No
Draw a dirt molecule with soap molecules
heads facing out
tails inside dirt
What does bleach do?
kill germs
