Aim: To prove that oxygen is evolved during photosynthesis.

Apparatus: Beaker, funnel, test tube, water, Hydrilla plants.
Procedure: Take a few pieces of Hydrilla plant. Keep a wide mouthed funnel into a beaker with water. Place the Hydrilla pieces inside the funnel. Carefully invert a test tube filled with water over the narrow end of the funnel. Keep the entire apparatus in sunlight for 2 to 3 hours.
Observation: After some time you will observe small gas bubbles coming out of the leaves of Hydrilla. These bubbles collect at the end of the test tube. Collect more gas and then take out of the test tube by closing its mouth with the thumb. Test the gas by introducing glowing splinter. The splinter glows and burns more vigorously.
Conclusion: From the above experiment, it is clear that oxygen is evolved during photosynthesis.
Precautions:
1. See that the twigs of Hydrilla plant are inside the funnel.
2. while you are testing for oxygen, see that outside air does not enter test tube.
3. For the experiment use only glass funnel and beaker.