method

• 1. add some sodium hydrogen-carbonate powder to a beaker and dissolve in water
• 2) place a piece of pondweed in the bottom of the beaker
• 3) if necessary, weigh down the pondweed with a paperclip
• 4) can also place an upturned boiling tube filled with paper over the top to make bubbles easier to see
• 5) place the lamp 5cm from the pondweed and switch on, now allow the pondweed to acclimatise for 5 minutes
• 6) count the number of bubbles produced in 1 minute
• 7) repeat steps 4 to 5 with different distances