Practical: evolution of oxygen from photosynthesis

• Background

  • We can demonstrate the evolution of oxygen (from the process of photosynthesis) using water plants such as Elodea or Cabomba types of pondweed
  • As photosynthesis occurs, oxygen gas produced is released 
  • As the plant is in water, the oxygen released can be seen as bubbles leaving the cut end of the pondweed
• apparatus

  Apparatus

  • Beaker
  • Water plant
  • Funnel
  • Boiling tube
  • Splint
  • Bunsen burner (for the oxygen test)
  • Heat proof mat
• method

  • Take a bundle of shoots of a water plant
  • Submerge them in a beaker of water underneath an upturned funnel
  • Fill a boiling tube with water and place it over the end of the funnel
  • As oxygen is produced, the bubbles of gas will collect in the boiling tube and displace the water
• results and analysis

  • Show that the gas collected is oxygen by relighting a glowing splint