Demonstrating the production of oxygen during photosynthesis

Variables:

Fixed: volume of water, amount of pondweed, size of beaker/test tube/funnel, temperature

Manipulated: light intensity

Responding: amount of oxygen released in a certain amount of time

Apparatus:

• Canadian pondweed
• Glass beaker
• 250 ml water
• Thermometer
• Test tube
• Funnel
• Support (to keep the funnel off the bottom of the beaker. This allows the water to circulate)
• Lamp (light source)

  

Method:

1. Collect apparatus.
2. Fill beaker with 250 ml water.
3. Take temperature of water and record.
4. Place Canadian pondweed in funnel (with leaves facing base of funnel) and attach support to the base of the funnel.
5. Place funnel inside beaker.
6. Fill test tube to the brim with water.
7. Place your finger on the top of the test tube, hold it every close to the beaker of water, and then tip it upside down so that the open end is underwater placed on top of the funnel and there is no air in the tube.
8. Leave beaker in darkness for minimum of 5 minutes to ensure that no photosynthesis occurs.
9. Place beaker one metre away from the lamp. Measure the distance to make sure.
10. Place apparatus in light.
11. Any oxygen released by the plant should rise to the bottom of the test tube.
12. Leave experiment for roughly 30 minutes.
13. Check amount of oxygen collected and record results.
14. Move experiment 10 centimetres closer to the light source and repeat steps 1 to 13. Record results.