Purpose
To show that oxygen gas is released during photosynthesis
Additional information
Plants use sunlight and carbon dioxide present in air to produce food for itself; one of the by products of this chemical reaction is the formation of oxygen. The fact that oxygen aids combustion makes it easy to identify this gas.
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Required materials
- Glass beaker
- Water-weed
- Funnel
- Test-tube
- Water rich in carbon dioxide
- Glowing splinter to test gas generated
Estimated Experiment Time
Approximately 10 minutes to set up the apparatus and 5-8 hours to carry out the observations
Step-By-Step Procedure
- 1.
Fill a glass beaker with water rich in carbon dioxide - 2.
Place green water-weed (Elodea or Ceratophyllum) in this beaker - 3.
Place a funnel over the plant (encasing it) - 4.
Invert a test-tube filled with water over the funnel - 5.
Leave this set-up undisturbed in bright sunlight
Note
Bubble carbon dioxide gas through water before using it to fill up the glass beaker for best results.
Observation
Bubbles of colorless gas are formed on the leaves after some time and are seen to rise and collect in the upper, closed part of the test-tube. On testing the gas by placing a glowing splinter in the tube, it bursts into flames.
Result
The splinter caches fire because the gas released by the leaves is oxygen; hence oxygen is released during photosynthesis.
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