Suspension (chemistry)
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WaterAndFlourSuspensionLiquid.jpg
In chemistry, a suspension is a dispersion (mixture) in which a finely-divided species is combined with another species, with the former being so finely divided and mixed that it doesn't rapidly settle out. In everyday life, the most common suspensions are those of solids in liquid water.
A suspension of liquid droplets or fine solid particles in a gas is called an aerosol. In the atmosphere these consist of fine dust and soot particles, sea salt, biogenic and volcanogenic sulfates, nitrates, and cloud droplets.
The term is widely used in Earth sciences to describe the transport of sediments in rivers and oceans. Particles that are suspended remain suspended so long as energy (provided in the form of a current) is applied to the system. The amount of energy determines the maximum size of particle that can be suspended. All particles down to colloidal size will settle in the absence of energy (aggitation).
It is important to distinguish suspensions from solutions which do not separate over any period of time because the intermolecular forces between the different types of molecules are of similar strength to the attraction between molecules of the same type. Entropy is then sufficient to keep a solution mixed without the need for the external input of energy which a suspension requires.
Common examples
- Mayonnaise is a colloidal suspension of water and vinegar droplets in edible oil, emulsified by egg yolk
- Gelatin is a suspension of water in a matrix of protein
- Butter is a suspension of water in butterfat globules
- Ice cream is a suspension of microscopic ice crystals in cream
- Orange juice is a suspension of orange pulp in water
- Mud or muddy water, is where soil, clay, or silt particles are suspended in water.