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Martyn F. Chillmaid/Science Source
Filtration
Heterogeneous mixtures composed of
solids and liquids are easily separated by
filtration.
Filtration
is a technique that uses a
porous barrier to separate a solid from a liquid.
As
Figure 21
shows, the mixture is poured
through a piece of filter paper that has been
folded into a cone shape. The liquid passes
through, leaving the solids trapped in the filter
paper.
Distillation
Most homogeneous mixtures can be separated by distillation.
Distillation
is a physical separation technique that is based on differences in the boiling points of
the substances involved. In distillation, a mixture is heated until the substance with the
lowest boiling point boils to a vapor that can then be condensed into a liquid and
collected. When precisely controlled, distillation can separate substances that have
boiling points differing by only a few degrees.
Sublimation
Mixtures can also be separated by
sublimation,
which is the process
during which a solid changes to vapor without melting, i.e., without going through the
liquid phase. Sublimation can be used to separate two solids present in a mixture when
one of the solids sublimates but not the other.
Chromatography
Chromatography
is a technique that separates the components of a
mixture dissolved in either a gas or a liquid (called the mobile phase) based on the
ability of each component to travel or to be drawn across the surface of a fixed substrate
(called the stationary phase).
For example, chromatography paper is a stationary phase with a solid substrate. During
paper chromatography, the separation occurs because the various components of the
mixture in the liquid mobile phase spread through the paper at different rates. Compo-
nents with the strongest attraction for the paper travel slower.
Figure 21
As the mixture passes through the filter, the solids
remain in the filter, while the filtrate (the remaining liquid) is
collected in the beaker.
Get It?
Compare and contrast
the mobile phase with the stationary phase in
chromatography.
Get It?
Predict
the result of trying to use filtration to
separate the components of salad dressing.
imagine using salad dressing that is a
mixture of oil, vinegar, and spices and a
paper filter for the procedure.
Lesson 4 • Mixtures of Matter
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