GREENHOUSE LAB
EXPERIMENTAL FOUNDATIONS OF GLOBAL CLIMATE CHANGE
BROUGHT ON BY CARBON DIOXIDE POLLUTION
STUDENT VERSION:
PART 1..........................1-10
PART 2.........................11-14
PART 3.........................15-17
TEACHER INFORMATION PAGES:
PART 1........................18-26
PART 2........................27-28
PART 3........................29-30
UV-Vis Instructions...........31-33
EXPERIMENTAL FOUNDATIONS OF GLOBAL CLIMATE CHANGE
BROUGHT ON BY CARBON DIOXIDE POLLUTION
PART 1
STUDENT HANDOUT
ARE LIVING ORGANISMS SOURCES OR SINKS FOR
CARBON DIOXIDE GAS?
Purpose: To use the color indicator bromthymol blue to determine
if plants, animals and decomposers release carbon dioxide gas and
to determine if plants absorb carbon dioxide gas.
Background information: Are living organisms a source of carbon
dioxide gas? Anything in nature, whether living, dead, or never
alive (like a rock) is considered a source if it releases carbon
dioxide into the atmosphere. Conversely, anything living or
nonliving that takes up or absorbs carbon dioxide gas from the
atmosphere or water is considered a sink (because like a sink in
your home, it acts like a "holding reservoir" for carbon dioxide
gas). This investigation involves the detection of carbon
dioxide gas. How can you detect the presence of a gas that is
colorless, odorless and tasteless? One method is through the use
of a chemical indicator called bromthymol blue. Bromthymol blue
is normally a blue liquid. If a small amount of carbon dioxide
is added to it, the liquid turns blue-green to green. High
levels of carbon dioxide gas cause the liquid to turn yellow. If
the carbon dioxide is removed, the liquid will return to the blue
color. The use of the spectrophotometer can quantify the color
change.
Materials (per group):
test tube rack
9 medium test-tubes
1 hole stopper,
connector and tubing
3 cotton balls
Scissors
Masking Tape
Rubber stoppers
Drinking Straw
Pasteur Pipet
Paper cup or beaker
0.1% Bromthymol Blue Solution
0.005% Bromthymol Blue solut’n
Vinegar
Baking soda
Yeast Solution
Elodea Plant
Plastic spoon
Aluminum foil
Metric ruler
Forceps
Light Source
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Procedure:
Part A: Detecting the presence of Carbon Dioxide
1.
Place two test tubes in the rack and label them A and B.
2.
Fill test tube A 1/4 full with vinegar.
3.
Fill test tube B 1/4 full with 0.005% bromthymol blue
solution. Record its color in Table 1.1, Part A, "Initial
Color".
4.
Wrap a 1" x 1" piece of aluminum foil around the point end of
a pen or a pencil. Twist the foil at the pointed end of pen
of pencil so that you have created a little "cup" that will
hold the baking soda. See Figure 1.1.
5.
Using a plastic spoon, fill the aluminum "cup" half full with
baking soda. See Figure 1.2.
6.
Tilt the test tube at an angle that will allow the "cup"
filled with baking soda to slide down into the test tube with
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vinegar so that the "cup" does not get any vinegar into the
"cup". See Figure 1.3.
7.
Place a cotton ball into test tube A about 1 cm from the top.
Then, place the rubber stopper (with tube attachment) into
test tube A. See Figure 1.4.
8.
Submerge the free end of the rubber tube into the bromthymol
blue solution of Test Tube B. Place a cotton ball at the top
of test tube B to hold the tubing in place. See Figure 1.5.
Your completed set-up should look like Figure 1.6. Before
continuing predict what color the bromthymol blue solution
will be after the baking soda mixes with the vinegar. Record
your prediction in Table 1.1, Part A, "Predicted results".
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10. Rock test tube A from side to side (do not shake up and down)
mixing vinegar with baking soda. See Figure 1.7.
11. Note the production of gas (bubbles of carbon dioxide gas,
CO2). After three minutes of bubbling in test tube B, record
the color of the solution in Table 1-1, Part A, "Observed
results".
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Part B: Determining if plants are a source for carbon dioxide.
1.
Place two clean test tubes in the rack and label one tube C
and the other D. Place a 5.0 cm segment of Elodea (the
aquarium plant) into the bottom of tube D. You may need to
push the plant down with a pencil to get the plant to the
bottom of the test tube.
2.
Fill test tube D with enough 0.005% bromthymol blue solution
to cover the Elodea plant. Fill test tube C to the same
level. Test tube C should contain only bromthymol blue
solution. Label each test tube with your name and contents
(masking tape may be used), and seal with rubber stoppers.
3. Wrap each tube separately in a sheet of aluminum foil so that
no light gets into the tube. Label with masking tape with your
name. Store tubes per your instructor's directions. Predict the
color of the bromthymol blue solution in each tube after 24
hours. Record the color in Table 1.1, Part B, "Predicted
results".
4.
After 24 hours in the dark, unwrap your tubes and note the
color of the liquid in each tube. Record the color in Table
1.1, Part B, "Observed results". You may find it helpful to
place a sheet of white notebook paper behind the tubes to
compare the colors. It may also be helpful to remove the
Elodea from the test tube.
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Part C: Determining if decomposers are a source of Carbon
Dioxide.
1.
Place two clean test tubes in the rack and label one E and
the other F. Fill both test tubes about 1/4 full of 0.005%
bromthymol blue. Record the color of the solution in Table
1-1, Part C.
2.
Using a Pasteur pipet, add 10 drops of yeast solution to tube
F. Add no yeast solution to tube E. With masking tape,
label each tube with your name and contents of each tube, and
seal tubes with rubber stoppers.
3.
Predict the color of the bromthymol blue solution in each
tube after exposure to the yeast. Record the color in Table
1.1, Part C, "Predicted results".
4.
Place tubes in teacher-designated area.
5.
At the end of the period, note the color of the liquid near
the bottom of each tube. Place a sheet of white paper behind
the tubes if necessary. Record the color in Table 1-1, Part
C, "Observed results".
Part D: Determining if animals are a source of Carbon Dioxide.
1.
Place about 50 mL of distilled water in a beaker. Place one
drop of the water on a spot plate or glass slide. Add one
drop of 0.005% bromthymol blue solution and note the color.
Record the color of the liquid in Table 1-1, Part D, "Initial
color".
2.
Predict the color change that the bromthymol blue test will
cause in the distilled water if you blow bubbles into the
water. Record your "Predicted Results" in Table 1-1, Part D,
"Predicted results".
3.
Exhale gently through a straw into the water so that your
breath bubbles through the water. Do this for several
minutes, then test by placing one drop of the water on a spot
plate or glass slide and adding one drop of 0.005% bromthymol
blue solution. Note the color. If the water does not test
yellow, continue exhaling into the beaker for another minute
or two, and test again.
4.
Record the color of the liquid in Table 1-1, part D,
"Observed Results".
Save the distilled water that you exhaled into for part E.
5.
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Part E:
Determining if plants are a sink for carbon dioxide.
1.
Fill 3 test tubes equally with the solution from part D.
Label the test tubes G, H, I.
2.
To test tubes G & I, add a 5.0 cm sprig of Elodea plant. Use
your straw to push the plants down to the bottom of the test
tubes. Seal the tubes with a rubber stopper.
3.
Seal test tube H with a rubber stopper (NO PLANT).
4.
Wrap test tube I entirely with aluminum foil to make it light
tight.
5.
Place all three test tubes in a rack. Expose the rack of
test tubes to a light source for at least 24 hours.
6.
For each of the 3 test tubes predict the color of the
solutions when tested with bromthymol blue at the end of the
24 hour experimental period. Record in Table 1-1, "Predicted
Results."
7.
After 24 hours, uncover the foil wrapped test tube and add
ten drops of 0.1% bromthymol blue solution to each test tube
(G,H,I). Compare the shades of color by holding test tubes
against a white background. Record your results in Table 11, "Observed Results".
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Observations:
Table 1-1 DATA CHART
PART
TUBE
Part A
Detection of
CO2
Tube B
Brom Blue
+ gas from
Tube A
Part B
Plants as
source of
CO2
INITIAL
COLOR
PREDICTED
RESULTS
OBSERVED
RESULTS
Tube C
Brom Blue
only
Tube D
Brom Blue
+ Elodea
Part C
Decomposers
(Yeast) as
source of
CO2
Tube E
Brom Blue
only
Part D
Animals as
source of
CO2
Cup
Brom Blue
+ Exhaled
Breath
Tube F
Brom Blue
+ Yeast
Tube G
Liquid
from Pt. D
& Elodea
Part E
Plants as
sinks for
CO2
Tube H
Liquid
from Pt. D
& no plant
Tube I
Liquid
from Pt. D
+ Elodea
in dark
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Discussion/Conclusion:
1.
List the organisms in this lab that were found to be a source
for carbon dioxide?
2.
Explain how one can experimentally detect the presence of
carbon dioxide.
3.
Are plants a source of carbon dioxide?
evidence?
4.
Are animals a source of carbon dioxide?
evidence?
5.
Are decomposers a source of carbon dioxide?
evidence?
6.
What is the purpose of having only Bromthymol Blue in test
tubes C and E?
What is your
What is your
What is your
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7.
Why did the bromthymol blue turn light-green when you blew
into the blue solution?
8.
How are you certain that light itself is not responsible for
the bromthymol changing back to the blue color?
9.
Explain the reason for the color observed at the end of the
experiment in test tube I.
10. Are plants a sink for carbon dioxide?
do you have? Explain.
What observed evidence
11. Presently, certain countries are cutting down thousands of
square kilometers of forests. Explain two ways this activity
affects the amount of CO2 in the atmosphere?
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