Use carbonated soda to explore solubility of a gas
Jean Weaver, Ph.D.< [email protected]>
The Prairie School
Racine WI 53402
Purpose
bottles and their contents (are the bottles the same size, is
there the same amount of soda in each, are there bubbles
present in either bottle, etc.). Write down your observations
in the table below.
To illustrate the effect of temperature and pressure on the
solubility of a gas in a liquid.
Applications
2.
Slowly open each bottle, one at a time. Observe and
compare what you hear and see happen in each bottle.
Write down your observations.
3.
Slowly pour a little of each soda into your cups. Again,
observe and compare. Write down your observations.
4.
Finally, taste the warm and the cold soda and record your
observations.
Solubility, gases, solutions, Henry’s Law
Materials
∙ two identical, unopened 20 oz sodas in plastic bottles per lab
group (any kind will work, but colas and root beer produce
the most noticeable effects)
∙ drinking cups
∙ cooler containing an ice-water slurry
∙ lab oven or food service warming oven
Homework Questions
1.
Which soda, the warm or the cold one, had more dissolved
carbon dioxide? List all the ways that you know.
Do not perform this experiment in a lab; try a classroom or a
cafeteria.
2.
What is the best way to store an opened bottle of soda so
that is doesn’t go flat quickly?
Preparation
3.
In order to make electricity, many power plants condense
steam by pumping cool river or lake water around the steam
pipes. The steam cools and condenses as its heat is
transferred to the water, which is then returned to the river
or lake. What impact does this warm water have on the fish
in the lake or river? (Hint: think about the solubility of gases
and what gas fish need to survive.)
Safety Precautions
Each lab group should bring in two sodas and drop them off well
before class (the day before you do this activity, or during the
morning). At least an hour before class, your teacher will place
one of the bottles in the cooler, the other in the oven. He or she
will heat the sodas gently so as not to rupture the plastic bottles.
Student Directions
1.
Without opening the bottles, observe and compare the
Disposal
Pour any remaining soda down the sink.
Observations
Before Opening
While Opening
After Opening
12 Chem 13 News/October 2007
Warm Soda
Cold Soda
Outcomes for soda lab (for the teacher)
Teacher comments
The way I do this experiment with my students is as an inquirybased lab where the kids follow my brief directions and have to
think about their own observations in order to draw their conclusions. Explaining the Theory section to them beforehand would
spoil all the fun — they would already know what is supposed to
happen and their conclusions would lack authenticity. Students
enjoy this lab; having soda in class is a bonus.
20th Biennial Conference on
Chemical Education,
July 27 – 31, 2008
Theory
The solubility of a gas in a liquid, such as CO2 in soda, is
proportional to the external pressure. Once the seal on a soda
bottle has been broken, the pressure decreases to match the
atmospheric pressure and gaseous CO2 begins to escape from
the solution as evidenced by bubbles and fizz. The solubility of
the CO2 is also inversely dependent on the temperature. A warm
bottle of soda has a larger “air” space at its top and bubbles and
fizzes more than a cold bottle of soda. Once opened and at
atmospheric pressure, a cold soda maintains its carbonation
longer than an identical warm soda.
Observations that your students might make include:
Observations
Before
Opening
While
Opening
After Opening
Warm Soda
- Bottle bulged
outward
- More “air” space
above soda
- Loud, long
“whssssh”
sound
- Lots of bubbles
rising to the top
- Had to close
bottle to keep it
from overflowing
- While pouring:
lots of fizzing
and foam, tall
head
- Tastes flat,
“bad”
Cold Soda
- No apparent
change
- Short, soft
“whsssh”
sound
- Some
bubbles, not
many
- While pouring:
soft fizz, small
amount of
foam in cup
- Tastes tangy,
fizzy, “good”
Answers to homework questions
1. The cold soda had more dissolved carbon dioxide. Proof:
the warm soda bottle bulged outward but the cold one
maintained its shape; the cold soda had a softer fizzing
sound and less gas was released when the bottle was
opened; the cold one produced less fizz when the soda was
poured into cups; and the cold soda did not taste flat but the
warm one did.
2. Sealed, in a cool place such as a refrigerator.
3. The temperature of the river or lake water increases which
causes the solubility of oxygen to decrease. As a result, the
fish have difficulty breathing and may die or at least
relocate. ∎
The Biennial Conferences on Chemical Education (BCCEs),
which are sponsored by the ACS Division of Chemical
Education, are the largest gathering of chemical educators in the
world and are designed for middle school science teachers,
secondary school chemistry teachers, and college chemistry
instructors. This conference emphasizes the improvement of
chemistry education at all levels, the modern developments in
chemistry and chemical education, and is highly respected in the
chemical education community.
Claire Baker, secondary education program chair, is putting
together a wonderful series of symposia for high school
teachers. Topics include Advanced Placement Chemistry,
Chemical Demonstrations, Before Five Years of Experience,
and Overview of College Credit Programs for High School
Students to name a few. There will also be symposia focused
on teacher preparation, continuing education, and building
bridges between secondary education and college programs. In
addition to all of the symposia, there will be hands-on workshops
and plenty of time to network with your colleagues.
More information about the conference is available at
http://bcce2008.indiana.edu. There is still time if you are
interested in organizing and submitting a symposium proposal —
the deadline is November 2, 2007. Since the BCCE is a time for
professional development, you should consider presenting a
paper or poster. Abstract submission opens November 15, 2007.
If you have any suggestions, ideas or questions about the
conference, please contact the organizers through our email
address, [email protected]. We look forward to seeing
YOU at the 20th BCCE in Bloomington, Indiana!! ∎
October 2007/Chem 13 News 13