Classification of colloids

hydrophilic colloids

A hydrophilic colloid molecule resembles water molecules and when dispersed in water, it hydrates. The hydrated colloids increase the viscosity of the system, thus improving the stability by decreasing the interaction between the particles and their tendency to settle; they may also have an inherent surface electric charge. The charge signal depends on the pH of the system and the chemical properties of the colloid.

hydrophobic colloids

A hydrophobic colloid has little or no propensity for water and does not change the viscosity of the system. The particles can take on a charge, due to the adsorption of electrolyte ions from the solution.