Emulsions

In-depth explanation of Emulsions

An emulsion is a colloid formed by dispersing one liquid as small droplets in another liquid with which it is immiscible. Two common types are oil in water, as in milk, and water in oil, as in butter. Emulsions are unstable on their own, because droplets coalesce and separate, so they need an emulsifying agent that stabilizes the interface between the liquids. Emulsifiers have one end that dissolves in each liquid, forming a layer at the boundary that prevents droplets from merging. Lecithin in egg yolk stabilizes mayonnaise, and soap stabilizes grease in water.

Going deeper: Emulsions

Key ideas: Types are tested by dilution or dye: an oil-in-water emulsion mixes with water and conducts electricity, while water-in-oil does not. The HLB scale of the emulsifier guides the type: high HLB gives O/W, low HLB gives W/O. Typical droplet sizes are 0.1 to 10 micrometres. Homogenization breaks droplets down for stability, as in milk.

Common mistakes and connections: Students think emulsions are solutions; they are two-phase systems that separate without a stabilizer. Another error is saying the emulsifier reduces the amount of oil; it only reduces interfacial tension. Creaming happens by density difference, while coalescence needs film rupture. Links to micelles, surfactants, colloids and the Tyndall effect.

Visualization of Emulsions

An emulsion disperses one liquid as droplets in another; oil-in-water (milk) and water-in-oil (butter) types need emulsifiers. The interactive lesson shows this as a live animation or chart.

Worked example and use case

Soap helps emulsify grease in water, allowing oily dirt to be washed away from dishes.

Where Emulsions fits in States of Matter & Solutions

Emulsions is topic 98 of 109 in States of Matter & Solutions.

Related topics

• ColloidsIntermediate
• Tyndall EffectIntermediate
• Brownian MotionIntermediate
• MicellesAdvanced
• Gels and SolsIntermediate
• AdsorptionAdvanced

Browse all 109 topics in States of Matter & Solutions