The Effects of Exercise on the Production of Carbon Dioxide

CLASS COPY

Introduction: Respiration is the process by which food molecules are broken down to release energy. The human body obtains energy through cellular respiration, which uses oxygen, breaks down the sugars and produces waste products of carbon dioxide and water. In humans, blood carries the carbon dioxide to the lungs where it is released from our bodies through exhalation.

Carbon dioxide (CO2) dissolves in water to form carbonic acid (H2CO3). Water will become more acidic as more carbon dioxide is added. As a result, phenolphthalein, an indicator solution, can be used to show the presence of carbon dioxide in water. An acidic solution can then be neutralized with a base such as sodium hydroxide (NaOH). By knowing the amount of sodium hydroxide needed to neutralize the acid, you can determine the amount of carbon dioxide in the solution.

Objective: SWBAT determine the effect of exercise on the production of carbon dioxide.

Materials: Stopwatch Straw 2 – 125 mL flasks Rubber Stopper NaOH solution Tape Phenolphthalien solution

Procedures:

1. Fill two 125 mL flasks with 75 mL of water. Label one flask as the control by placing a rubber stopper at the top of that one. 2. Add 5 drops of phenolphthalein to each flask. If the water does NOT turn PINK, add sodium hydroxide to the water ONE DROP AT A TIME until you obtain a light pink color. Swirl the container gently between the addition of each drop of sodium hydroxide. 3. WEAR YOUR GOGGLES! The first trial is done to examine how much CO2 is produced before exercising. Insert a straw into the other flask and blow gently into the water for 20 seconds. Try to breathe normally, but exhale slowly so that you do not splash the solution out of the flask. 4. Add NaOH to the flask, drop by drop, and swirl gently after each drop. COUNT the number of drops of NaOH needed to restore the pink color, comparing the color of the solution to that in the control flask. Record the number of drops of NaOH for all trials in Table 1. 5. Trial 2 involves minimal exercise. Jog for 1 minute and then repeat steps 3 and 4. 6. Trial 3 involves moderate exercise. Jog for 2 minutes and then repeat steps 3 and 4. 7. Trial 4 requires moderate exercise for a longer period of time. Jog for 3 minutes and then repeat steps 3 and 4. 8. If time permits continue with Trial 5 by jogging for 4 minutes repeating steps 3 and 4.

Safety: 1. Wear goggles 2. Follow all safety rules

Name: ______Date: ______Per: ______

The Effects of Exercise on the Production of Carbon Dioxide Objective: Determine the effect of exercise on the production of carbon dioxide.

BACKGROUND: Cellular respiration is the process by which food molecules are broken down to release energy. The human body obtains energy through cellular respiration, which uses oxygen, breaks down the sugars and produces waste products of carbon dioxide and water. In humans, blood carries the carbon dioxide to the lungs where it is released from our bodies through exhalation.

Carbon dioxide (CO2) dissolves in water to form carbonic acid (H2CO3). Water will become more acidic as more carbon dioxide is added. As a result, phenolphthalein, an indicator solution, can be used to show the presence of carbon dioxide in water.

When a solution is prepared containing both phenolphthalein and sodium hydroxide (NaOH), the solution will turn pink. The gradual addition of carbon dioxide will result in the solution turning clear. The now acidic solution can then be neutralized with the base, sodium hydroxide. By knowing the amount of sodium hydroxide needed to neutralize the acid, you can determine the amount of carbon dioxide in the solution.

ENGAGEMENT: Answer the following questions in a complete sentence. 1. What waste product of respiration is released via human lungs?

2. What will happen to water when CO2 is added to it?

3. What chemical indicator will be used to show the presence of CO2 in water?

4. What substance will be used to neutralize the effect of CO2 on water?

5. By adding the “neutralizing” substance, what will that tell us?

Hypothesis: ______

Procedure: Design an experiment to test your hypothesis. Created a detailed procedure in the space below. Be sure to include a detailed materials list. EXPLORATION: During-Lab Observations: Table 1. Number of NaOH drops required to neutralize the CO2 produced during exercise. Resting 1 min. jog 2 min. jog 3 min. jog 4 min. jog

Group Results

**On a separate sheet of paper, create a class data table to display the CO2 produced during exercise.

EXPLANATION: Answer the following questions in a complete sentence 1. What does the color change in step 3 (when the runner breathes into the pink flask) indicate?

2. What is the function of the NaOH in this lab?

3. How did the CO2 production change as the level of exercise was increased? Why?

EVALUATION: Complete the following on a separate sheet of graph paper. 1. Graph the respiration data. 2. Write a thorough scientific conclusion of the experiment that you performed. EXTENTION: Complete the following using complete sentences. 1. Write the general equation for respiration, which shows CO2 as a waste product:

2. Within which cellular organelle does this process occur? Why would human muscle cells contain many more of this organelle than skin cells?

3. Use the graph to predict the amount of CO2 that would be produced at the end of six minutes of exercise. Express your answer in terms of the number of drops of NaOH added.

4. Discuss what would happen to the pH of cells if CO2 was NOT carried away from the cells by the circulatory system and exhaled after being passed into the lungs.

5. Evaluate your experimental design. Things to consider: Where there details missing from your design? Did you include a control? Did you indicate the need for multiple trials? Did you provide enough detail in your materials list? Did you consider science safety? What additional background research would you do?