1. Glucose + Oxygen → Carbon dioxide + Water + Energy (as ATP)
Cellular Respiration
C6H12O6+ 6 O2 → 6 CO2 + 6 H2O
Glucose + Oxygen → Carbon dioxide + Water + Energy (as ATP)

2. Bromothymol Blue
When you add bromothymol blue to water, it turns blue, indicating that the pH is near 7.
When carbon dioxide dissolves in water, carbonic acid is produced. The pH of the water is shifted from neutral to more acidic.

3. To compare your CO2 output under different conditions, you will exhale through a straw into a flask filled with bromothymol blue.
The CO2 that you exhale will dissolve in the water, and gradually acidify it. You'll be able to see the pH indicator change color as this happens.
By measuring how long it takes for the pH change to occur, you will be able to measure of the amount of CO2 in your breath.
The less time it takes for the color change to happen, the more CO there was in your breath.

4. PROCEDURE
Assign one person to be the timer, and one person to perform the experiment.
Using a straw blow into the bromthymol blue solution until you see the color change from blue to green or yellow. Be careful not to inhale the solution!
Time how long it takes for the solution to change color and write down the time it took for the color change
Run in place for 1 minute. You should feel a little winded when you are finished
Using the same straw but the 2nd beaker, blow into the solution and see how long it takes for the solution to change from blue to green or yellow.
Write down the time it took for the color change