While a suspension will separate out a colloid will not. Colloids can be distinguished from solutions using the Tyndall effect. Light passing through a colloidal dispersion, such as smoky or foggy air, will be reflected by the larger particles and the light beam will be visible.
A hydrocolloid can simply be defined as a substance that forms a gel when it comes in contact with water. Such substances include both polysaccharides and proteins. Colloids are unlike solutions because their dispersed particles are much larger than those of a solution. The dispersed particles of a colloid cannot be separated by filtration, but they scatter light, a phenomenon called the Tyndall effect.
Colloids are often confused with true homogenous solutions because the individual dispersed particles of a colloid cannot be seen. When light is passed through a true solution, the dissolved particles are too small to deflect the light. However, the dispersed particles of a colloid, being larger, do deflect light see figure below.
The Tyndall effect is the scattering of visible light by colloidal particles. You have undoubtedly "seen" a light beam as it passes through fog, smoke, or a scattering of dust particles suspended in air. All three are examples of colloids. Suspensions may scatter light, but if the number of suspended particles is sufficiently large, the suspension may simply be opaque, and the light scattering will not occur. Listed in the table below are examples of colloidal systems, most of which are very familiar.
Some of these are shown below see figure below. The dispersed phase describes the particles, while the dispersion medium is the material in which the particles are distributed. Butter and mayonnaise are examples of a class of colloids called emulsions.
An emulsion is a colloidal dispersion of a liquid in either a liquid or a solid. A stable emulsion requires an emulsifying agent to be present. Mayonnaise is made in part of oil and vinegar.
Since oil is nonpolar, and vinegar is a polar aqueous solution, the two do not mix and would quickly separate into layers.
However, the addition of egg yolk causes the mixture to become stable and not separate. Egg yolk is capable of interacting with both the polar vinegar and the nonpolar oil. Explanation: Suspensions consist of more than one homogenous phase, for example, a suspension of clay particles in water consists of small solid particles suspended in liquid.
Related questions How are solution, solute, and solvent related? Why do solutions become saturated? How does temperature affect solutions? How does a solution differ from a colloid? How does buffering a solution change the solutions behavior? How does Benedict's solution change colour?
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