Breath Lab Directions
Materials needed:
4 beakers or cups filled half way with water
4 straws
Blue food coloring
Bromothymol blue carbon indicator
In one of the four cups, place three drops of Bromothymol Blue and mix so that it evenly distributes. In the other three
cups place food coloring so that it looks identical to the first cup.
This lab is set up as a demo, and you trick students into believing that they are participating in a “Bad Breath” lab
activity. Have four students volunteer for this lab, make sure to pick one really talkative student- they will be the guinea
pig.
Have students blow steadily through the straws into the solution for about two minutes. Caution students not to
accidentally drink or inhale the solution- go ahead and lie and tell them it is poisonous. After two minutes the guinea pig
cup will turn green. (Plan for 2 minutes of chaos). Settle the class and explain that the green cup actually had a carbon
indicator and begin the discussion of cellular respiration and its waste products.
Name: _________________________________________________ Date: ___________________________ Period: ___
Photosynthesis and Cellular Respiration
Cool Breath Lab: Cellular Respiration & the Carbon Cycle
What is the set up for the lab? _________________________________________________________________________
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What was the outcome and why? ______________________________________________________________________
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How does this mini lab tie into cellular respiration and Photosynthesis?
Claim
Evidence
Reasoning
Photosynthesis
vs.
Cellular Respiration
Photosynthesis
Cellular Respiration
Energy+6CO2 + 6H2O  6O2 + C6H12O6
6O2 + C6H12O6  6H2O + 6CO2 + energy
For this activity, you will balance the equation for photosynthesis to convert it to the chemical formula for
cellular respiration. What did you notice as you balanced the chemical formulas?
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Using what you know about photosynthesis and cellular respiration,
explain the image you see to the right.
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