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.