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Oxygen weed called Elodea can be used to collect oxygen gas which is given off by photosynthesis.
The following experiment can be carried out in the classroom. Alternatively if Elodea is not available some
results of oxygen gas collection have been provided.

Elodea is a common plant that can live in fish ponds. The results of collecting oxygen gas from Elodea were recorded in the following table.

A amp was placed at varying distances from the oxygen weed. The number of bubbles given off every 5 minutes were recorded.

Light Source Distance to Elodea – lamp Data
10 cm 15
20 cm 10
30 cm 5
40 cm 3
50 cm 1

Plot the data on a the graph below. Distance from lamp is on the x axis.


Answer the following questions in the space provided

  1. What assumption are we making about the gas?

2. What other variable must we check that must remain constant? Why?




 Extension Questions

nswer the following questions in the spaces provided. Explain why these things occur according to photosynthesis.
1. Why do potatoes stored in the dark grow shoots that are not green?



2. A plant was left in a darkened room and the leaves turned yellow. Explain why.



Extension Question
Oxygen is a waste product and carbon dioxide is plant food. Explain how this works with the animal kingdom.



This a print copy only activity.