3.4 LIGHT MY FIRE
(Level: 10 appl :: Photosynthesis)
Purpose: To see if oxygen is produced during
What You Need: 2 test tubes :: sodium bicarbonate :: 2
small beakers :: wooden splint :: 2 funnels :: aquatic plant such
as Elodea :: rubber stopper
What You Do:
- Insert freshly cut ends of the Elodea into the stem of one
- Fill both test tubes and funnels full of water. You can do
this by putting the whole apparatus (beaker, funnel, and test
tube) in a sink full of water.
- Arrange the material as shown in the diagram.
- Dissolve 2-3 cc (1/2 tsp) sodium bicarbonate in the water of
each beaker. This will supply the carbon dioxide needed for
- Shine a very bright light on the set-up for at least 48
hours. (More sodium carbonate can be added during the waiting
- Test the gas that collects to see if it is oxygen. Do the
test as follows:
- Fill the beaker full of water
- Lift the test tube off the funnel, but do not let any air
- Put a stopper in the mouth of the test tube
- Lift the test tube out of the beaker
- Turn the test tube upright. The gas should now be on top of
- Remove the stopper and quickly put the glowing splint into
the gas. (Have the glowing splint ready before you remove the
- Describe the gas that collected in the experimental test
- What did this gas do to the glowing splint.
- How can you be sure that the gas is oxygen and not just
- Why was a control needed?
Click here to see the answers to these questions.
Click here to see the list of activities for this unit.