1. Set up a boiling tube containing sodium hydrogencarbonate solution
2. Allow the tube to stand for a few minutes and shake to disperse any air bubbles that might form
3. Cut a piece of the pondweed, 8cm long
4. Use forcepts to place the pondweed in the boiling tube, without damaging it or causing the liquid to overflow
5. Position the boiling tube so that the pondweed is 10 cm away from the light source
6. Allow the boiling tube to stand for five mins
7. Count the number of bubbles emerging from the cut end of the stems in one min, repeat five times and record results
8. Calculate the average number of bubbles produced per min