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February 24, 1997


Plants and Oxygen: Breathing Easy


Purpose:

The student will understand that trees and plants produce a lot of the oxygen we breathe.

Grade level:

Second Grade

Essential Elements:

Acquire data through the senses. The student shall be given opportunities to: (B) observe properties and patterns of objects, organisms, and events in the environment; (E) explore the environment.

Objectives:

To quickly show students how plants produce oxygen.

Focus:

Hold up a plant and ask students if they believe that plants like this help us breathe.

Materials:

A clear, glass bowl of water (a small aquarium works well), a glass jar, a few water plants such as pondweed ( may be purchased at pet store)

Background:

The Earth's atmosphere today is a mixture of gases, water vapor, and a variety of solid particles and liquid droplets. In some respects, air differs from place to place around the globe. The air in a tropical rain forest is hot and steamy. People travel to the seaside to enjoy the "salt air." Visitors go to the Smokey Mountains in Tennessee view the bluish air. On a cold night in the Arctic the air feels particularly dry and "pure." Dry, filtered air is roughly 78 percent nitrogen, 21 percent oxygen, and 1 percent other gases. Most samples of natural air contain some water vapor as well. In a hot, steamy jungle, air may contain 5 percent water vapor, whereas in a dry desert or a cold polar region there may be almost none at all.

Procedure:

  1. Place the plants in a deep bowl of water.
  2. Fill the glass jar with water by lowering it on its side into the bowl, letting all trapped air bubbles escape.
  3. Turn the glass upside down to cover the plants.
  4. Leave the plants in a sunny place and watch what happens. You will not have to hold your breath for long. Oxygen bubbles from the plants will start rising toward the surface of the water! Eventually a pocket of oxygen will collect at the top of the jar.
  5. Explain to students that plants and trees release oxygen into the air. During the process of making food from carbon dioxide and water, trees and plants give off oxygen. Energy from the sun is used to change the carbon dioxide and water into food and release oxygen. This process is called photosynthesis.

Conclusion:

Cutting down too many trees could leave us breathless. Have students write about the experiment and tell how it works.

Note to teacher:

Plants need to be healthy and experiment needs to be done in a sunny location.


Acknowledgments:

Linda Abbott, Stephen F. Austin Universtiy Nacogdoches TES Course, 1994; Environmental Science, 1984, CBS College Publishing


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