required practical

• 1. Set up a boiling tube containing 45 cm3 of sodium hydrogencarbonate solution . let the tube to stand for a few minutes and shake to get rid any air bubbles that might form.
• 2. Cut a piece of the pondweed. The pondweed should be 8 cm long.
• • Independent variable – distance from the light source/light intensity.
  • Dependent variable – the number of bubbles produced per minute.
  • Control variables – concentration of sodium hydrogencarbonate solution, temperature, using the same piece of pondweed each time.