| how is a stable emulsion formed | when the hydrophobic fatty acid chains dissolve in oil while the hydrophilic hydroxyl groups dissolve in water |
| how are soaps formed | by the alkaline hydrolysis of fats and oils by sodium or potassium hydroxide by boiling under reflux conditions |
| what is formed by the alkaline hydrolysis of fats and oils | glycerol and three carboxylic acids known as fatty acids
under alkaline conditions the fatty acids immediately react to form water soluble ionic salts called soaps |
| how many soap molecules are made per molecule of glycerol during hydrolysis | three molecules of sap are made per molecule of glycerol |
| what is the catalyst during alkaline hydrolysis | alkalis such as potassium hydroxide or sodium hydroxide |
| what happens to the fatty acids formed during hydrolysis | they are changed into sodium or potassium salts (soaps) such as sodium stearate, in a neutralisation reaction
these salts are ionic and water soluble |
| describe the structure of soap | there is a hydrophobic tail and a hydrophillic head |
| describe the hydrophobic tail of a soap molecule | the long, non polar covalent hydrocarbon chain on the fatty acid gives rise to the hydrophobic part of the soap
this part of the soap is soluble in non polar compounds such as oil and grease (like dissolves like) |
| describe the hydrophilic head of a soap molecule | the ionic/polar group at the end of the soap molecule (the head) is hydrophilic
this means that the head of the soap molecule is soluble in ionic and polar compounds such as water but not in oil |
| how does soap work | the soap is added to the water, the soap molecules arrange themselves in grease and water (hydrophobic tails in grease and hydrophilic head in water)
agitation/scrubbing/shaking begins to separate the grease from the surface. The process continues to form micelles. These micelles are able to be washed away as they are suspended in water |
| what are micelles | balls of grease droplets in water |
| what is meant by hard water | a term used to describe high levels of dissolved metal ions |
| what happens when hard water is mixed with soap | it forms a precipitate (scum), reducing cleansing action |
| what are soapless detergents | substances like detergents with a hydrophilic head and hydrophobic tail
they remove oil and grease in the same way as soap |
| do soapless detergents form scum with hard water | no, therefore detergents are used in hard water areas as they do not form scum |
| what does an emulsion contain | small droplets of one liquid dispersed in another liquid |
| what can an emulsifier be used for | to prevent non polar and polar liquids from separating into layers |
| what does the addition of an emulsfier allow | for two otherwise immiscible layers to be mixed uniformly, dispersing an equal amount of each throughout the entire volume
this mixture is able to exist as a stable (non separating) emulsion for a reasonable time (known as shelf life) |
| how can emulsifiers for use in food be made | by reacting edible oils with glycerol
in the molecules formed, only one or two fatty acid groups are linked to each glycerol backbone |
| are the hydroxyl groups present in emulsifiers hydrophobic or hydrophilic | hydrophilic |
| are the fatty acid chains present in emulsifier hydrophobic or hydrophilic | hydrophobic |
| how is a stable emulsion formed | when the hydrophobic fatty acid chains dissolve in oil while the hydrophilic hydroxyl groups dissolve in water |
