Respiration Lab

Gas Exchange  Key Question: Will you exhale more CO2 if you hold your breath?  Initial Thoughts:

Evidence: Gas Exchange Lab  Indicators – chemicals that look different when exposed to other chemicals.  BTB – detects Carbon Dioxide, or CO 2  Blue = No CO 2  Yellow = CO 2 present  Demonstration with volunteers

Demo Results  Color of solution before: ___________  Color of solution after:_____________ Hypothesis: if, then, because format

Measuring CO 2 Procedure: 1. Each person will measure 10 ml of water in a graduated cylinder and pour into your plastic cup. 2. Add 3 drops of BTB into the cup, then pour into your own 1 gallon bag. 3. Remove the air from your plastic bag by slowly flattening it. Be careful not to spill any BTB solution out of the bag. 4. While keeping the air out of the bag, place a straw in the mouth of the bag and make an air-tight seal by holding it tightly around the straw. 5. Fill the bag with air from your lungs by blowing until the bag is fully inflated. 6. As you finish, pull out the straw, squeeze the bag tightly shut so no air escapes. 7. Holding the bag shut, shake the bag vigorously 25 times. 8. Pour the BTB solution from the bag into a clean, empty plastic cup.

Procedure contd… 10. To find out how much CO2 is in your breath: a) Add 1 drop of Sodium Hydroxide to your plastic cup b) Gently stir the solution and wait at least 10 seconds. c) Record in your science journal that you added 1 drop d) Compare the color of your solution to the control. Is it the same color as the control for at least 30 seconds? e) If your answer is no, repeat steps 10a-d 11. Record the number of drops it took to change your solution back to the same color as the control. 12. Now hold your breath for as long as you can, then exhale into the bag. 13. Repeat steps Record your lab group members numbers in your table, and find the mean. 15. Graph the data in a bar graph.

Data Table # of drops of NaOH Subject’s NameNormal BreathHeld Breath Mean:

Analysis Questions: 1. A) What was the manipulated variable? B) What was the responding variable? 2. What did the demonstration tell you about the exhaled breath of a human? 3. What does your data tell you about the amount of CO2 you exhale when you hold your breath?

Summary/Conclusion Minimum of 4 sentences  What was your hypothesis, and was it supported or not supported?  How did holding your breath affect the amount of CO 2 exhaled?  Explain your conclusions using your data as evidence.  How could you improve the design of your experiment? Make sure this is thoughtful and thorough.

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