Name ______Date ______
Mrs. G-M (300 Biology) Period ______
Effect of Exercise on Carbon Dioxide Release in the Human Body
Purpose:
To examine the effects of exercise on the amount of CO2 released by the respiratory system.
Introduction:
Carbon dioxide reacts with water to form carbonic acid; bubbling your exhaled air through water forms this acid. Bromthymol blue is an indicator that turns yellow in the presence of acid and will be used to show if carbonic has been formed.
By adding of sodium hydroxide (NaOH), a base, to the water you breathed into, the acid will be neutralized and the solution will turn back to blue. The more NaOH needed to turn the solution back to blue, then the more CO2 was exhaled.
Materials:
· goggles
· 100 mL graduated cylinder
· 125 mL flask
· water
· straw
· timer
· bromthymol blue (in dropper bottle or with separate dropper)
· 0.4% sodium hydroxide (NaOH) (in dropper bottle or with separate dropper)
o Caution: NaOH is caustic and may burn your skin/eyes! You MUST wear goggles & closed-toe shoes!
Part I: Control Data (Before Exercise)
Procedure:
1. Fill the graduated cylinder with 100 mL of water and pour the water into the small flask.
2. Add 8 drops of bromthymol blue solution to the water.
3. Record the appearance of the solution: ______
4. Place one end of the straw in the water and blow into the water for one minute – exhaling at the same rate. Caution: Do NOT inhale from the straw!
5. Record the appearance of the solution: ______
6. Remove the straw from the flask and set it on a paper towel. (Remember which end was in the solution!)
7. WHILE COUNTING, add ONE DROP of NaOH AT A TIME, to the water. Swirl the water while adding the drops. Once the solution changes back to blue, stop adding drops. If it remains blue for one minute, do not add any more NaOH. If it does not remain blue for one minute, continue adding one more drop at a time until it does remain blue for one minute.
8. Once the solution remains blue for one minute record the total number of NaOH drops needed : ______
Part II: Experimental Data (After Exercise)
Procedure:
1. Fill the graduated cylinder with 100 mL of water and pour the water into the small flask.
2. Add 8 drops of bromthymol blue solution to the water.
3. Record the appearance of the solution: ______
4. Put the straw back in the flask. (Be sure to put the same end back in the solution.)
5. Choose some sort of exercise to do and how long you are going to do it (and put that information in the first two blanks of your hypothesis below).
6. Hypothesize: If I ______for ______minutes, then my cells will produce __(more / less)__ CO2 (which will be exhaled through my respiratory system), because my cells are carrying out __(more / less)__ cellular respiration.
7. Perform your exercise.
8. Blow into the water for one minute – exhaling at the same rate. Caution: Do NOT inhale from the straw!
9. Record the appearance of the solution: ______
10. WHILE COUNTING, add ONE DROP of NaOH AT A TIME, to the water. Swirl the water while adding the drops. Once the solution changes back to blue, stop adding drops. If it remains blue for one minute, do not add any more NaOH. If it does not remain blue for one minute, continue adding one more drop at a time until it does remain blue for one minute.
11. Once the solution remains blue for one minute record the total number of NaOH drops needed: ______
12. Have your partner carry out the same procedures and then share data with each other.
a. Who did you share data with? ______
b. How many drops of NaOH did they need for their solution to remain blue before exercisizing? ______
c. How many drops of NaOH did they need for their solution to remain blue after exercisizing? ______
13. Construct a (double) bar graph to represent YOUR data and THEIR data (for both the control and experimental groups). Be sure to may a key to show which bars are for which person.
14. Answer the questions below:
a. How do you account for any differences between your data and the data of the person you shared with?
b. Predict how regular, daily exercise might change the amount of CO2 released by the body.
c. If an open container with a water and bromthymol blue solution were left in a room full of people, what changes would you expect to see? Explain your reasoning.