Physical aspects - Prior knowledge - Introduction - Foams and emulsions
3 important questions on Physical aspects - Prior knowledge - Introduction - Foams and emulsions
What 4 things do emulsions and foams have in common?
- Both systems have a large amount of interface between the phases
- Surface active components needed to stabilise interfaces
- Both meta-stable systems (slowly evolving towards complete separation). Not in stable equilibrium, can seem stable over certain period of time
- Evolve by the same mechanisms (aggregation, coalescence, Ostwald ripening, creaming) --> unstable
What are 2 difference between emulsions and foams?
- Density difference between the two phases is much larger in foams (air-liquid)
- Droplet size is much smaller in emulsions (um in emulsion vs. Mm in foam)
As a result of these two differences destabilisation, such as creaming, is much faster in foam
What are 2 different types of emulsions?
- Oil-in-water (O/W): oil droplets in a continuous water phase, e.g. Milk, mayonnaise, salad dressing
- Water-in-oil (W/O): water droplets in oil phase, e.g. Butter, margarine (fatter)
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