|What is the difference between "solution" and
A solution is mixed together at a molecular
level, while a suspension is mixed at a larger
level. The easiest way to test this is by
letting a solution or suspension sit for many
days. A solution (like water and salt) will not
have any separation. The salt will stay mixed. A
suspension (like powdered chalk in water) will
separate out after some time. An emulsion is
like a suspension -- it will separate out --
but the things being mixed are two liquids (like
A solution is a homogeneous mixture of two
components. This means that wherever you look
at the solution, it appears the same throughout
the entire container. This is different than a
suspension, which is a heterogeneous mixture of
two components that will separate if left long
For example, if you dissolve salt in water, it
will make a solution, and you can't separate the
two, no matter how long you leave it. In contrast,
if you mix mud and water, the mixture will look
cloudy, but if you let it sit long enough, the mud
will eventually settle and you'll have clear water
on top, and mud sitting on the bottom.
In a solution, the dissolved substance is
interacting chemically with the solvent and
dissociated into its component molecules or ions.
In a suspension, the particles are not
and may still be part of crystals or other larger
structures than just the molecules.
In a solution, the solute molecules (the
solid or liquid in solution) are surrounded by
solvent molecules (the liquid in which you are
dissolving the solute). In this case, the
solute is evenly distributed in the solvent. In a
suspension, particles or crystals of the solute
remain – this is generally because the
interaction of the solvent or solute with itself
is much stronger than the interaction between the
solute and solvent. Suspensions are generally
unstable and the particles will grow bigger over
time. Solutions, though, are stable over time –
unless there’s a drastic change in temperature or
there’s not enough solvent to dissolve the solid.
A great example of solutions and suspensions is
an oil and vinegar salad dressing. Vinegar is a
solution of acetic acid dissolved in water –
notice that you can’t see any particles in the
liquid. When you add oil to vinegar and shake
hard, you’ll see small pockets of oil in the
vinegar and vice versa, all mixed together in a
suspension. If you wait a while, the two liquids
will separate into layers. Now try adding some
salt and shaking – which layer will it dissolve
in? In the water layer, the salt dissolves to
form a solution. In the oil layer, the grains of
salt remain suspended and not dissolving.
Most salad dressing that you buy is stabilized
with an emulsifier (also called a surfactant) than
allows the suspension to last longer.
Emulsifiers are molecules that have a side that
likes water (hydrophilic) and a side that likes
oil (hydrophobic). When mixed in salad
dressing, they coat the surface of the oil pockets
and keep them from reforming into an oil layer
after you shake the dressing. Some examples of
emulsifiers in your kitchen are the mayonnaise
(the egg proteins) and mustard. Add a little of
either of these to your oil and vinegar mixture
before and you’ll notice that the layers take much
longer to reform than before.
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