NAME ______________________________________ DATE _________________ PER _________ MS. DAY/H. BIOLOGY
LAB #3: CARBON DIOXIDE AND EXERCISE LAB
Background Information: In this lab, you will examine the effects of exercise on how much carbon
dioxide is release by your respiratory system. Bromothymol blue is a chemical indicator that changes color as the
pH of a solution changes. It is yellow in acidic solutions and blue in basic and neutral solutions. When carbon
dioxide is dissolved in water, I creates carbonic acid, pH~5.7. One of the products of cellular respiration is carbon
dioxide. As cells produce CO2 in cellular respiration, it is carried by our blood cells to our lungs where it is exhaled
(removed). Therefore, bromothymol blue turns yellow in the presence of carbon dioxide. When sodium hydroxide
is added to the solution it will turn back to the bromothymol blue color. The more sodium hydroxide (NaOH) that
needs to be added to turn the water back to blue, the more carbon dioxide there is in the solution. Read the
procedure then answer the questions below.
Purpose (What is the problem we are investigating?):
_____________________________________________________________________________________________
Hypothesis (How exercise will affect your body’s production of carbon dioxide?):
What is the independent variable? _______________________________________________
What is the dependent variable? _________________________________________________
Materials:
50 & 10 mL graduated cylinder
250 mL Erlenmeyer flask
800 mL of water
bromothymol blue solution
50 mL 0.4% NaOH solution
straw
timer
Procedure:
1.
Select 1 person to be your timer, 1 person to be your recorder/set-up person, and 2 people to be the workout person (We will call then Person #1 and Person #2).
2.
Measure out 30ml of water (tap water is fine) and pour into a clean Erlenmeyer flask. Give to person #1.
3.
Repeat steps #1-2 but give flask to person #2.
4.
Person #1 and person #2 will add 5 ml of bromothymol blue solution to the water in his/her flask.
5.
Place one end of the straw in the water and have person #1 and person #2 blow in their water for one
minute. Exhale always at the same rate. DO NOT inhale from the straw!
6.
At the end of your minute add sodium hydroxide (NaOH) solution to the water (drop by drop) – make sure
to swirl the water solution as you adding drops. Count the number of drops needed for the solution in the
cylinder to turn blue and remain blue.
7.
Record your data for person #1 and #2 in the data table.
8.
Empty and rinse the flask. Repeat steps 1-3.
9.
Have BOTH person #1 and person #2 perform a low impact exercise (walking) for 2 minutes.
10. At the end of the 2 minute period, immediately repeat steps 4-6.
11. Repeat steps 1-3.
12. Have BOTH person #1 and person #2 perform a medium impact exercise (jogging) for 2 minutes.
13. Again repeat steps 4-6 immediately at the end of your 2 minutes.
14. Repeat steps 1-3.
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15.
16.
Lastly, have BOTH person #1 and person #2 perform perform a high impact exercise (jumping jacks with
arms!) for 2 minutes.
Again, repeat steps 4-6 immediately at the end of your 2 minutes.
Results:
Title : ____________________________________________________________________________
Number of 0.4% Sodium Hydroxide
Number of 0.4% Sodium Hydroxide
Exercise
Solution Drops (Person #1)
Solution Drops (Person #2)
Rest
(no exercise)
Exercise 1
(walking)
Exercise 2
(jogging)
Exercise 3
(jumping jacks)
Construct a graph representing your data for EACH person. Remember to use the type of graph will best display
your data.
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Conclusion:
Write a conclusion that includes the following points. A conclusion is written in full, complete
sentences and is no less than 2-3 paragraphs in length. Try to write cohesive paragraphs that flow
together, not jumping from one point to the next.
 Hypothesis is rephrased (not copied and pasted) and the conclusion states whether or not
the hypothesis is supported or not.
 SPECIFIC EXAMPLES OF DATA are cited in the conclusion to support or refute the hypothesis
 What is the relationship between exercise and the amount of carbon dioxide exhaled?
 What mechanisms in the body explain these results?
 Explain any possible experimental errors and analyzes why the possible errors would have
caused a deviation in your recorded data.
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Post Lab Questions:
1. What does it mean when the solution in lab turned yellow/green?
2. What does it mean when the solution in lab turned blue?
3. What happens to carbon dioxide when it mixes with water?
4. Carbon dioxide is a waste product of a process called cellular respiration. What is cellular respiration?
Why is it important for organisms to complete this process?
5. How is this lab related to our class discussion/lecture about the respiratory system and homeostasis?
6. What was the control groups used in this lab? Why is it the control group?
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