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…