Creating Carbon Dioxide

Hypothesis:

Human respiration produces carbon dioxide.

Materials:

Bromothymol Blue solution (BTB)

2 Balloons of different color of at least 7 inch diameter

2 Drinking straws

Bicycle pump

Masking tape

2 50 mL graduated cylinders

Procedure:

1. Pour 25 mL of BTB into each of the two graduated cylinders and set them aside.
2. Put a straw into the neck of each balloon and secure with masking tape.
3. Inflate a balloon by blowing through the straw and pinch the balloon closed at the neck.
4. Use the bicycle pump to inflate a second balloon of a different color and pinch the balloon closed at the neck.
5. Release the amount of air to make it the same size as the first balloon and then seal with a twist tie.
6. Place the straw of one balloon into the BTB in the graduated cylinder so the opening of the straw is in the liquid of the cup.
7. Release the gas in the first balloon  to allow the gas to bubble through the BTB.
8. Repeat steps 6 and 7 with the second balloon.

 

Observations:

Compare the color of the liquid in the two cups. Record your observations in the space below.

Graduated cylinder with gas from air pump- _____________________________________________________

Graduated cylinder with gas from exhalation- ______________________________________________________

Conclusion:

Did your observations support your hypothesis? Defend your answer.

______________________________________________________________________________________________

______________________________________________________________________________________________

Follow up:

On a separate page name one variable in this experiment that you could investigate in a follow up experiment. Describe how you could carry out this experiment.

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