Suspension (chemistry)
In
chemistry, a
suspension is a
colloidal 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. In the absence of additional energy (agitation), all particles down to
colloidal size will eventually settle out into a distinct phase.
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.
*
Mayonnaise is a colloidal suspension of mostly
water and a few
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*
Mud or muddy water, is where
soil,
clay, or
silt particles are suspended in water.
*
colloid*
sol*
emulsion*
turbidity*
settleable solids*
sediment transport*
solution
