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Oxygen Production
D. Crowley, 2008
Oxygen Production
To know that oxygen is produced during photosynthesis
Tuesday, April 18, 2023
Photosynthesis
During photosynthesis what is produced?
carbon dioxide + water → oxygen + glucose
How can we test that gas produced is oxygen?
light
Experiment
Collect: • elodea; • glass funnel; • lamp; • large beaker; • marker pen; • narrow bung; • ruler; • stop watch
Experiment
1. Measure 1cm3 from the end of the funnel, and make a mark
2. Set up the apparatus, but do not put the bung on yet (make sure the water level is above the top of the funnel)
3. Place the lamp 10cm away from the beaker, wait 2 minutes, then place the bung in and start the stop watch
4. Stop the stop watch when the gas bubbles have filled the end of the funnel down to your mark – write down how long this took in seconds
5. Repeat this experiment, moving the distance the lamp is from the beaker (record how far away the lamp is)
Results
Distance between lamp & beaker (cm)
Time taken for end of funnel to fill with gas (seconds)
Distance 1 (10cm)
Distance 2 (20cm)
Etc…
Graph & Analysis
Draw a line graph of your results and write down your findings – what relationship was there between the distance of the lamp and beaker and the amount of gas produced?
Rate Of Oxygen Production When Light Away From Elodea Is Changed
0
50
100
150
200
250
0 10 20 30 40 50 60 70 80 90 100Distance Between Lamp & Beaker (cm)
Tim
e T
aken
Fo
r F
un
nel
To
Fill
Wit
h G
as
(sec
)
Evaluation
How accurate was this experiment? How could you improve this experiment next time?
What affect does the lamp have on the water? How can heating the water give a false result?
* Heating the water can cause oxygen to come out of solution
Oxygen
How can we prove that the gas produced is oxygen?
Oxygen should relight a glowing splint…