Chapter 1 – Distilling Cherry Coke
CP Chemistry
Name _____________________________
Date ____________ Class Pd __________
Separating Mixtures – Distillation and Chromatography
Background
In order to study the chemical properties of materials, it is important to establish whether they
are pure substances or mixtures. Often heterogeneous mixtures can be easily identified because
of different regions are easily seen by the naked eye. Distinguishing homogeneous mixtures
(also called solutions) from pure substances can be more difficult. Homogeneous mixtures have
uniform physical characteristics such as density, color, and boiling point. You are already
aware that you can separate the components of a mixture through physical processes or
changes. Parts A and B below explore two different and common physical processes for
separation of mixtures.
Part A – Distillation of Soft Drinks
Many compounds used in food and medicine come from
plant or animal extracts. For example, paclitaxel (Taxol®),
an anticancer drug, was extracted from the bark of the
Pacific yew tree. Living systems, including plants, are
complex mixtures containing many substances. The
extraction of just one of those substances may require many
steps and produce very small quantities of material. This
lab simulates the extraction of specific compounds from a
mixture through distillation. This separation process can
occur because the different components of the mixture have
different boiling points. Four components - - 1) carbon
dioxide, 2) water, 3) coloring, and 4) artificial cherry
fragrance - - can be identified.
Part B - Paper Chromatography
Chromatography is a method for analyzing complex
mixtures (such as ink) by separating them into the
chemicals from which they are made. Chromatography is
used to separate and identify all sorts of substances in
police work. Drugs from narcotic to aspirin can be
identified in urine and blood samples, often with the aid of
chromatography. Because molecules in ink have different
characteristics (particle size and solubility), they travel at
different speed when pulled along a piece of paper by a
solvent (in this case, water.) When water flows through the
ink, the molecules of each one of the colors behaves
differently, resulting in a chromatogram. See how many
different colors you can identify in each sample of ink.
Procedure & Materials:
Part A – Distillation of Soft Drinks
Materials & Set Up:
1)
2)
3)
4)
5)
6)
7)
Hot plate
Electrical cord (you won’t have to get this, it is already attached to the hot plate)
Large Test Tubes (you need 2 of these)
100 mL of cherry cola in a 250-mL Erlenmeyer flask
Rubber Tubing
Distillate (collected during experiment)
Ice Bath in 400-mL beaker
Also needed but not numbered:
* Rubber Stopper with one hole
* Glass L-shaped tube
* Goggles
* Limewater, used to detect carbon dioxide (turns cloudy in the presence of CO2), about 1
inch in one of the test tubes
5
3
6
4
1
7
2
Procedure:
1. Assemble the extraction apparatus by carefully setting a 250-mL Erlenmeyer flask containing
approximately 100 mL of cherry cola on a hot plate. Secure the flask using a ring stand & test
tube clamp.
2. Record your observations about the appearance of the cherry cola before heating.
3. Place the rubber stopper, with its glass tube and rubber tubing, into the flask.
4. Turn on your hot plate to a medium-low setting (3 or 4).
5. Place the end of the tubing into a small test tube containing limewater so that the rubber tube is
submerged in the limewater. (You only need about an inch of limewater in the test tube.)
6. As the cherry cola gently warms and bubbles lightly, the first component of the mixture leaves
the liquid as a gas and will pass through the limewater. Observe the resulting changes in the
limewater and record them.
7. After the limewater has reacted, turn off the hot plate.
8. Obtain a 400-mL beaker of ice and prepare an ice bath using a small amount of water.
9. Place a clean test tube into the ice bath.
10. Insert the rubber tubing from the distillation apparatus into the test tube. This time the tubing
does not need to be very far down the test tube, just enough to collect drops of liquid from the
rubber tubing in the test tube.
11. Turn on your hot plate to the highest setting and continue heating vigorously on high heat until
only about half of the original volume remains in the flask. This should take from 15-20
minutes. Continue to make observations of your system throughout the heating process.
** While you wait for the system to heat, proceed to the setup for Part B. **
12. Compare the liquid distillate (sight and smell with wafting) to the liquid remaining in the flask.
13. Compare the liquid distillate to the original cola mixture.
14. Wash all your glassware, rinse the distillation tubing and wipe down your lab bench. Be sure
your hot plate has cooled before wrapping the cord around it.
(Part B on back)
Part B – Paper Chromatography with Ink (each group member does a chromatogram)
Materials:
* Filter paper strip
* 400 mL beaker
* Pencil
* Marker
* Stirring Rod
* Water
Procedure:
1. Using PENCIL, draw a line about 1 cm from the bottom of the strip. Write your initials at the
top of the strip.
2. Draw a small dot of ink with the provided pen along the line at the bottom of the strip.
3. Hold the strip inside the 400-mL beaker so that it almost touches the bottom. Fold the top end
of the strip over a glass-stirring rod. The strip should now be suspended inside the beaker, but
NOT touching the bottom.
4. Carefully add water to the beaker until it reaches the bottom of the paper strip, just below the
ink mark. Be sure the ink stays above the water and the paper stays in the water.
5. Allow the water to soak up the strip. Record observations about what happens to the ink mark.
6. When the water has risen within 1 cm of the top of the strip, remove the paper from the beaker
and hang it on the line to dry.
Chapter 1 – Distilling Cherry Coke
CP Chemistry
Name _____________________________
Date ____________ Class Pd __________
Separating Mixtures – Distillation and Chromatography
Data & Observations
Part A – Distillation:
Appearance of original cola
mixture
Original appearance of
limewater
Size of bubbles in flask
when cola is on mediumlow heat
Changes in the limewater
Size of bubbles in flask
when cola is on high heat
Observations of flask while
boiling
Appearance of distillate in
test tube (including aroma)
Appearance of remaining
liquid in flask (including
aroma)
Part B – Chromatography:
Tape
chromatogram
here
Original ink color
Appearance of final
chromatogram
Notes about other
chromatograms (include
initials of whose
chromatogram it is)
Post-Lab Questions
I understand that this is an INDEPENDENT assignment. I will not ask other students, the internet
or tutors for help answering these questions. I will only discuss this assignment with Mr. Sandoe,
should I have any questions.
X_________________________
Part A – Distillation:
1. What physical property allows for separating the components of a mixture through distillation?
2. Based on the evidence you collected from observing the limewater, what was one of the
components in the cherry cola mixture? Reference your observation in your answer.
3. Why was it important to have the collecting test tube in an ice bath? What type of physical change
was occurring when the vapors hit the test tube? (Think about states of matter).
4. Explain how the liquid distillate in the test tube was different than the liquid that was still remaining
in the flask at the end of the experiment. Use specific observations and physical properties.
5. What flavorings/fragrances were you able to detect at the end of the experiment (from either the
flask or the test tube containing the distillate)?
6. There are four components of the cherry cola mixture that can be identified. List the four
components and also provide evidence from the lab that suggests each of these components was
actually present.
a.
b.
c.
d.
Part B –Chromatography:
7. What two physical properties (or characteristics) allow for separation of mixtures by
chromatography?
8. Describe what the chromatogram would look like for an ink that only has one component.
Thoroughly explain your response.
9. Describe the appearance of a chromatogram when the ink is made from a mixture of components.
10. Based on your experiment and other classmates’ experiments, which of the inks contain only one
type of dye molecule? List the initials of any student who only had one ink molecule in the dye
tested & the color of the marker they tested.
11. Based on your experiment and other classmates’ experiments, which inks used in the lab mixtures
of dyes? List the initials of any student who only had mixtures of ink molecules in the dye tested
& the color of the marker they tested.
12. Does the color of ink determine whether or not it is a mixture of dyes? Explain how you reached
this conclusion, using examples from the lab.