So you know that when life forms on that planet breath out, it changes bromothymol blue from
yellow to blue. With your given materials, write a procedure below that will use your prior
knowledge of photosynthesis and cellular respiration to prove what gas those life forms exhale.
Materials:
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Bromothymol blue solution in beaker (in blue, not yellow)
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Straw
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Elodea (aquatic plant)
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If needed, a light source in the spaceship/classroom
Procedure:
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Once you are finished with your experiment, answer the following questions.
1. Compare the reactants of the photosynthesis equation to the products of the equation for
respiration. What do you notice?
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2. Compare the reactants of the respiration equation to the products of the
photosynthesis equation. What do you notice?
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3. What color does the bromothymol blue solution turn after you exhale into the solution?
Why does it change that color?
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4. What is the purpose of photosynthesis?
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5. What were your results? Explain your answers knowing what you know about the solution,
why it changes color, and what plants need to do photosynthesis.
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