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PHOTOSYNTHESIS

PHOTOSYNTHESIS. What is the role of CO 2 in photosynthesis?. Plants USE carbon dioxide to carry out photosynthesis. We can determine the presence of CO 2 in water by using an indicator called BTB ( bromthymol blue). BTB is neutral (7).

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PHOTOSYNTHESIS

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  1. PHOTOSYNTHESIS

  2. What is the role of CO2 in photosynthesis? • Plants USE carbon dioxide to carry out photosynthesis. • We can determine the presence of CO2 in water by using an indicator called BTB (bromthymol blue). BTB is neutral (7). • If CO2 is dissolved in water it will form carbonic ACID. • BTB turns YELLOW in acids and GREEN in bases. • Let’s demonstrate….

  3. NOW LET’S TEST… Procedure: • Label 4 test tubes A, B, C, & D • Fill each test tube1/2 full with water • Add 20 drops of Bromthymol Blue (BTB) indicator to each test tube • What color is the water in the test tubes? • What is the pH of the water? • 4. Use a straw and gently blow into test tubes A & B • What color do you think the water will turn after blowing into it?

  4. This is how it’s done…

  5. Procedure Continued • Place a sprig of ELODEA in test tubes A & C. • Screw tops onto test tubes and let sit under a grow light for 24 hours. • What process is the Elodea going to be carrying out?

  6. STARTING OBSERVATIONS Water, CO2, Elodea, yellow Water, CO2, yellow Water, Elodea, blue Water

  7. Hypothesis What do you think will happen in each of the test tubes after 24 hours? TEST TUBE A Plant will photosynthesize…use the CO2…tube will turn back blue TEST TUBE B Nothing will happen…no plant…tube will remain yellow TEST TUBE C Nothing will happen…plant present…water present…no CO2…tube will be blue TEST TUBE D Nothing will happen…no plant…no CO2…this is CONTROL tube…still blue • Write your predictions on your data sheet.

  8. The next day...

  9. Conclusion • Test Tube A: • Water is blue… • plant removed CO2…photosynthesized • Test Tube B: • Still yellow… • No plant present to remove CO2 • Test Tube C: • Water is yellow… • plant released CO2…carrying out respiration • Test Tube D: • No change…control

  10. ANALYSIS • Write a conclusion about what you have learned about the relationship between carbon dioxide and photosynthesis. • In which tube did photosynthesis take place? What evidence supports your answer? • Explain what you think would have happened if test tube 1 were placed in the dark for 24 hours instead of the light. • Which test tube was the control tube? • Name 3 constants in the experiment • What was the independent variable in the experiment? (there were 2 different indvar)

  11. The Scientific Method What was the independent variable? What were some constants?

  12. What affects the rate of photosynthesis? • Sunlight • Amount of CO2

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