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Solutions, Suspensions, Colloids, and Dispersions
The Distinguishing Characteristics That Set These Similar Things Apart
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Solutions, suspensions, colloids, and other dispersions are similar but have characteristics that set each one apart from the others.
A solution is a homogeneous mixture of two or more components. The dissolving agent is the solvent. The substance that is dissolved is the solute. The components of a solution are atoms, ions, or molecules, making them 10-9 m or smaller in diameter.
Example: Sugar and water
The particles in suspensions are larger than those found in solutions. Components of a suspension can be evenly distributed by mechanical means, like by shaking the contents but the components will eventually settle out.
Example: Oil and water
Particles intermediate in size between those found in solutions and suspensions can be mixed in such a way that they remain evenly distributed without settling out. These particles range in size from 10-8 to 10-6 m in size and are termed colloidal particles or colloids. The mixture they form is called a colloidal dispersion. A colloidal dispersion consists of colloids in a dispersing medium.
Example: Milk
Other Dispersions
Liquids, solids, and gasses all may be mixed to form colloidal dispersions.
Aerosols: Solid or liquid particles in a gas
Examples: Smoke is solid in a gas. Fog is a liquid in a gas.
Sols: Solid particles in a liquid
Example: Milk of Magnesia is a sol with solid magnesium hydroxide in water.
Emulsions: Liquid particles in a liquid
Example: Mayonnaise is oil in water.
Gels: Liquids in solid
Examples: Gelatin is protein in water. Quicksand is sand in water.
Telling Them Apart
You can tell suspensions from colloids and solutions because the components of suspensions will eventually separate. Colloids can be distinguished from solutions using the Tyndall effect. A beam of light passing through a true solution, such as air, is not visible. 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.
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