Video Transcript
Which of the following methods is
the most appropriate for separating a suspended solid from a liquid? (A) Filtration, (B)
crystallization, (C) evaporation, (D) distillation, or (E) centrifugation.
A good example of a solid suspended
in a liquid is sand suspended in water. The sand is not dissolved in the
water. As long as the mixture is stirred,
the sand will be dispersed throughout the water. If we stop stirring the mixture,
the sand particles are large enough that they will settle to the bottom of the
container. To answer this question, we need to
determine which of the methods provided is the most appropriate for separating this
type of mixture. Let’s examine each of the
separation techniques.
Filtration is a separation
technique ideal for separating mixtures that contain an insoluble solid and a
liquid. In this separation technique, the
mixture is poured through a filter. Large solid particles will be
trapped by the filter paper, while liquids and dissolved ions will pass through into
the flask. As suspended solids are insoluble
solids, it seems as though answer choice (A) is the correct answer. But just to be sure, let’s take a
look at the other answer choices.
Crystallization is a separation
technique primarily used to separate a soluble solid from a liquid. In this technique, the mixture is
gently heated until some of the liquid evaporates and small crystals begin to form
on the surface of the liquid or the edges of the evaporating dish. The solution is then allowed to
cool and the resulting crystals are collected to separate the soluble solid from the
liquid. As suspended solids are not soluble
in a liquid, crystallization cannot be the answer to this question.
Evaporation is very similar to
crystallization and is used to separate a solid from a liquid. During evaporation, the mixture is
heated until all of the liquid has evaporated, leaving behind the solid. While this method could be used to
separate a suspended solid from a liquid, it is more time-consuming than
filtration. Because of this, evaporation is
typically used to separate a soluble solid from a liquid rather than an insoluble
solid. So while evaporation could be used
to separate a suspended solid from a liquid, it is not the most appropriate
method.
Distillation is a separation
technique used to separate two miscible liquids that have different boiling
points. As this method is used to separate
two liquids and not a solid and a liquid, distillation cannot be the answer to this
question.
Centrifugation is a separation
technique used to separate solid particles from a liquid. The mixture is spun at a high speed
inside of a centrifuge. The spinning forces the more dense
particles to the bottom of the container, while centrifugation could be used to
separate a suspended solid from a liquid, it works best when the volume of the
mixture is small, the solid particles are very fine, and the solid easily clumps
together when spun. So centrifugation is not
necessarily the most appropriate method for separating a suspended solid from a
liquid.
Therefore, the method that is the
most appropriate for separating a suspended solid from a liquid is filtration,
answer choice (A).
