Colloidal solutions are mixtures in which insoluble, microscopic particles of one substance are dispersed through a different medium. The suspended particles are often referred to as the dispersed phase whereas the medium in which these particles are suspended is called the continuous phase. The phenomenon in which incident beams of light are scattered by colloidal particles is called the Tyndall effect. Several colloidal solutions are translucent due to this effect.
Classification
Colloidal solutions can be classified based on the dispersion medium and the dispersed phase. For example, fog/mist is a colloidal solution in which a liquid is dispersed into a gaseous medium. A few other types of colloidal solutions are listed below.
- Solids dispersed in gas. Example: smoke.
- Colloidal solution of a gas in a liquid. Example: foam.
- Liquid-liquid colloid. Example: milk.
- Solid-liquid colloid. Example: blood.
Alternately, colloidal solutions can be classified into hydrophilic and hydrophobic solutions. Hydrophilic (or reversible) colloidal solutions are attracted by water and hydrophobic (or irreversible) colloids are repelled by it.
Interactions Between Colloidal Particles
- The particles in a colloidal solution can hold electric charges and are, therefore, subject to electrostatic interactions such as attraction and repulsion.
- Fluctuations in electron densities or any bond dipole moments can result in permanent or induced dipoles in the colloidal particles. This implies that these particles are subject to Van Der Waals forces.
- As per the 2nd law of thermodynamics, the entropy of an isolated system always increases. Therefore, entropic forces play an important role in the interaction between the particles in a colloidal solution.
To conclude, colloidal solutions are mixtures containing a dispersed phase and a dispersion medium. There exist several types of colloidal solutions, ranging from liquid-liquid colloids to solid-liquid colloids. These mixtures can be either hydrophilic or hydrophobic in nature. Several forces such as electrostatic forces and Van Der Waals forces have a role to play in the interactions between the colloidal particles. To learn more about colloidal solutions, subscribe to the BYJU’S YouTube channel and enable notifications.
