Science project

Comparison of Carbon Dioxide Production Before and After Exercise



  1. Place 60 ml of water (1/4 cup) in beaker #1.
  2. Add 8-10 drops of bromothymol blue indicator, also known as BTB, to beaker #1.
  3. As BTB is exposed to carbon dioxide (CO2) it changes color from blue to a yellow or green color. After placing the BTB in the water do not allow it to sit very long before proceeding.
    1. Partner 1: Carefully watch the color of the solution. As your partner begins breathing into the solution begin the timer. When you detect a color change stop the timer.
    2. Partner 2: Begin breathing gently through a straw into the solution in beaker #1 (blowing bubbles). Do not blow with too much force as it can cause the solution to bubble out of the beaker.
    3. Record the time in Table 1 as Trial 1.
  4. Repeat steps 1-3 for Trial 2 using beaker 2.
    1. Average Trial 1 and Trail 2 times. Record as Average Time.
  5. Wash and dry both beakers.
  6. Partner 2 now exercises for 60 seconds. This needs to be activity that causes the heart rate and breathing to increase.
  7. Repeat steps 1-4, but record your findings as Trial 3 and Trial 4.
  8. Compare the average times of "Before Exercise" and "After Exercise."
  9. Was there a significant change? Why or why not?     
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