What is colloid ?
A colloid is a type of heterogeneous mixture, when two or more substances are mixed. A colloid mixture is formed with dispersed particles in a dispersion medium. Particles and medium are insoluble but they can not be separated from each other.
A colloid mixture has the following properties:
- The particles are very small (between 1 and 100 nanometers), they can not be seen by the naked eye.
- The particles cannot be filtered, they cannot be separated from the dispersion medium.
- This is a heterogeneous mixture
Types of colloids
Colloids mixtures can be classified in five main types : aerosols, foams, emulsions, sols and gels.
An aerogel is formed by adding liquid particles to a gas medium. Solid aerosols are formed by adding solid particles to the gas medium. Usually the gas medium can be air.
Hairspray, perfume and fog are examples of aerosols. Smoke, smog, dust in the air, volcanic ash are examples of solid aerosols.
Foams are formed by adding gas particles to a liquid medium. Solid foams are formed by adding gas particles to a solid medium.
Whipped cream, bubble bath, and fire retardant are examples of foams.
Emulsions are colloids formed by mixing liquid particles an a liquid medium. These substances don’t perfectly mix.
Mayonnaise, milk, and salad dressing are examples of emulsions.
Sols combine solid particles with a liquid medium. Solid sols combine solid particles with a solid medium. Solid sols are not as common as sols.
Blood, Ink, Paint, Mud are examples of sols. Glass, Gemstones are examples of solid sols.
Gels are colloids formed by adding liquid particles to solid medium. If gels are heated, they will become a sol.
Toothpaste, jam, cheese, and gelatin are examples of gels.