Heterogeneous Mixtures: Components do not mix, e.g., oil and water.
Suspensions:
Heterogeneous mixtures with large particles visible to the naked eye.
Example: Mud and water.
Colloids Defined
Colloids (Colloidal Dispersion): Mixtures that lie between a suspension and a homogeneous solution.
Particle size: Larger than ions/small molecules but smaller than suspension particles.
Characteristics: Particles can scatter light (Tyndall effect), causing a cloudy appearance.
Examples of Mixtures
Solutions: Saltwater (homogeneous)
Colloids: Milk, fog, smoke (cloudy appearance due to light scattering)
Suspensions: Mud in water (cloudy mixture with visible particles)
Components of Colloids
Dispersed Phase: Particulate component present in small amounts.
Dispersion Medium: Substance in which the particulate is dispersed.
Phases can vary:
Solid dispersed in gas (smoke)
Liquid dispersed in gas (clouds, fogs)
Liquid dispersed in liquid (milk, mayonnaise)
Liquid dispersed in solids (jellies, gels)
Gas dispersed in liquid (foams, whipped cream)
Preparation of Colloids
Breaking down larger particles: e.g., paint pigments.
Combining smaller molecules: e.g., water droplets in clouds.
Spontaneous colloid formation from substances like gelatin or starch in water.
Emulsions
Emulsions: Colloids formed by forcibly blending two immiscible liquids.
Example: Oil in vinegar (mayonnaise) or butterfat in water (milk).
Emulsifying Agent: Prevents coalescence of droplets (e.g., casein in milk, egg yolk in mayonnaise).
Electrical Charges in Colloidal Particles
Colloidal particles may carry an electrical charge, which helps keep them dispersed.
Charged particles can be removed using electrodes in a colloidal dispersion.
Electrostatic Precipitator: Device that attracts charged particles to electrodes, removing them from mixtures (used in industrial processes and air filters).
Summary
Understanding colloids is crucial as they differ from solutions and suspensions in particle size, appearance, and methods of preparation.
Colloids have diverse applications in everyday products and industrial processes.