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Chemicals: |
trichloroethylene (Carbo-sol from Sunnyside), mineral
spirits, water, food coloring. All chemicals can be bought at
hardware
stores or grocery stores. |
Materials: |
test tube, test tube caps, pipettes, test tube rack,
necessary safety supplies |
Note: |
Methylene chloride or 1,1,1-trichloroethane will also work
for trichloroethylene. Hexane will work for mineral spirits
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Procedure:
- Using a pipette add a small amount of
trichloroethylene to a test tube. A small amount
is 2-3 cm in height. Talk about it.
- Using a pipette very gently add a small but different
amount of mineral spirits to the surface of the trichloroethylene. Point
out the boundary and talk about this and get responses. Although
these two
will mix if shaken, they will stay separate if added gently.
- Carefully add one drop of a water solution of food
coloring to the test tube. It will float in the middle.
Talk about this and get responses. Add drops of solutions
of different colors of food coloring. If you are careful,
you may see several drops of varying colors floating side by
side.
- Using a pipette slowly drop in water drop by drop
allowing everyone to see the process and get responses as this
happens. Add enough
water until the two clear liquids are clearly separated.
- Ask what will happen if this is shaken. Then cap the
test
tube and shake vigorously. Ask for responses.
- If the colored water is on the bottom, add enough
trichloroethylene until it reverses. If the colored
water is on the
top, add enough mineral spirits until it reverses.
The mineral spirits will
have to be added to the bottom layer by pushing the
pipette through the
colored water and injected directly to the bottom layer. The
trichloroethylene will make the organic layer more dense, and
the mineral spirits will make it less dense, each affecting the
final position of the water layer and the organic layer in the
test tube.
Topics that can be discussed are density, miscibility, meniscus,
etc
----Contributed
by Frank Salter, Mark Twain Section
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