A colloid is a type of mixture in which one substance (called the dispersed phase) is evenly spread out in another substance (called the dispersion medium) with particle sizes larger than those in a true solution but smaller than those in a suspension.
- The particle size in colloids ranges from 1 nanometer (nm) to 1000 nanometers (nm).
- Colloidal particles are too small to be seen with the naked eye, but large enough to scatter light (Tyndall effect).
- They do not settle down on standing, so colloids are stable mixtures.
- They cannot be separated by ordinary filtration but can be separated by special methods like dialysis or ultrafiltration.
Key Properties of Colloids:
- Show Tyndall effect (scattering of light).
- Exhibit Brownian motion (random movement of particles).
- Cannot be separated by normal filters.
- Appear homogeneous to the naked eye but are actually heterogeneous at the microscopic level.
Examples of Colloids:
- Milk (emulsion of fat in water).
- Fog and clouds (liquid droplets in air).
- Smoke (solid particles in air).
- Jelly (liquid in solid).
- Paints, butter, whipped cream.
In short, a colloid is a heterogeneous mixture where fine particles of one substance are dispersed in another, with particle sizes between those of true solutions and suspensions.