SOLUTIONS VS. MIXTURES - LAB
Discover the difference between solutions and mixtures.
Solids are readily separated from liquids by passing the mixture through
a filter, a barrier with many small openings. This method is called
filtration. This is a simple method for separating sediment from water
in the course of the treatment of water for drinking purposes, because
the particles of sand and clay making up the sediment do not pass
through the filter.
Chemists keep containers of pure
chemicals called reagents on their shelves. Reagents are used in many
lab test to identify unknown substances or to conduct experiments.
Since reagents are known substances, they can help discover unknown
The iron sulfate that is in the solution
passes through the filter paper for the simple reason that the smallest
units of iron sulfate and the smallest units of water are much smaller
than the holes of the filter paper. The particles of white material are
too large to pass through the filter paper. Chemists use filters with
different sized holes.
The original mixture - the tablets
dissolved in warm water, that you filtered is called a suspension
because some of the material, the neutral component was suspended in
water. When you shake a suspension, it looks cloudy. True suspensions
eventually settle if you allow them to stand long enough, and you can
then separate the components by pouring off the solution that remains on
top. The residue remains on the bottom. Filtering is a faster way of
separating a filtrate from its residue.
Put the tablets in the measuring cup. Cover with about 1/2 cup of
water. Stir. Notice that the dark outer coating of the tablet comes
off and stains the water. Soak the tablets until the coating is
completely dissolved. Rise the tablets under the faucet. They should
be white. Rinse out the cup, fill it with about 3/4 cup of warm water,
and put the tablets in the cup. Stir until the tablets break up. The
white powdery material that does not dissolve is a neutral material used
by pharmaceutical firms in the manufacturing of the tablets.
To collect your iron sulfate solution and
separate it from the white powder, filter the mixture. Open the coffee
filter. Set the funnel in the jar. Stir the mixture well, then pour it
into the filter. The material that passes through the filter is called
the filtrate. The material trapped by the filter is called the
residue. Let the filtrate drain into the jar. Cover the jar and label