Breathe In, Breath Out

JoAnn Brooks-Williams Overton Elementary
221 E. 49th Street
Chicago IL 60615
(312) 535-1420

Objectives: Student will see that plants take in carbon dioxide. Student will see that plants need sunlight to absorb carbon dioxide. Materials Needed: aquatic plants test tube rack bromthymol blue 0.01% grow light water dropper straws saran wrap test tubes OR clear plastic cups Strategy: 1. Label test tubes or cups with A, B, C. Put 5 cm of water in each. Use dropper to add several drops of bromthymol blue. Mix. 2. Place a straw in test tube A and blow as you exhale. When the solution turns yellow, stop. 3. Break off two pieces of the aquatic plant and place one piece each in test tubes A and B only. Plant must be covered by the solution. Seal the three test tubes with saran wrap. 4. Put test tubes A and C in very bright sunlight or under a grow light. Put test tube B in a dark place. 5. Check the test tubes for a color change after 20 minutes. Make a record of the results. Test tube Beginning Color Ending Color A ___________ _____________ B ___________ _____________ C ___________ _____________ Performance Assessment: Students will be able to answer the following questions: 1. What gas was released when we exhaled as we blew into the bromthymol blue solution? 2. Why did the solutions in the test tubes change color? 3. At the end of the experiment, what happened to the solution in test tube A? Why? Test tube B? Why? Test tube C? Why? Conclusion: Green plants take in carbon dioxide while in the presence of sunlight. Objective: Students will demonstrate that plants release oxygen and water vapor during photosynthesis. Materials Needed: soil spiderwort plants (wandering jew) test tubes microscopes aquatic plants microscope slides and cover plates water 2 liter pop bottle coleus plants clear plastic cups dropper sunlight or grow light Strategy: 1. Tear off the leaf of a spiderwort plant in a circular direction to expose the lower transparent layer of the leaf. Place it on the microscope slide, put a drop of water on it, then cover it with a slide cover. Examine it under the microscope to find the stomata (holes through which CO2,
oxygen, and water vapor enters and exits the leaf).
2. Place a few aquatic leaves in a test tube of water. Turn it upside
down into the clear plastic cup of water. Place it in the sun or under a grow
light. Watch for the release of tiny oxygen bubbles.
3. Cut about 2.5 inches off of the top of a 2 liter bottle. Take the
black opaque bottom off. Fill the bottom with soil. Put a rooted coleus
plant in the soil. Water lightly. Turn the clear top upside down over the
plant. Place the terrarium in sunlight or under a grow light. Observe the
release of water vapor as it collects on the sides of the bottle.

Performance Assessment: 1. Describe the leaf's stomata or draw a picture of it. Are they opened or closed? 2. Why did we need sunlight for test tubes? terrariums? 3. What would have happened if the test tubes or terrariums had been placed in a dark place? 4. What gases are released during photosynthesis? 5. Describe oxygen. Describe water vapor. 6. Explain how the respiration process in plants and animals benefit each other. Conclusion: Green plants release oxygen and water vapor in the presence of sunlight.
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