A colloid is a type of mixture that appears to be a solution but it is actually a mechanical mixture. A colloidal system consists of two separate phases: a dispersed phase (internal phase) and a continuous phase (dispersion medium). In a colloid, the dispersed phase is made of tiny particles or droplets that are distributed evenly throughout the continuous phase. The size of the dispersed-phase particles are between 1 nm and 1000 nm in at least one dimension. Such particles are normally invisible even with a microscope;their presence can be confirmed with the use of an ultramicroscope or an electron microscope. Homogeneous mixtures with a dispersed phase in this size range may be called colloidal aerosols, colloidal emulsions, colloidal foams, colloidal dispersions, or hydrosols. The dispersed-phase particles or droplets are largely affected by the surface chemistry present in the colloid.
