Lab on Photosynthesis

Aim: To test what effect CO2 concentration has on the rate of photosynthesis; by placing an Elodea plant in water solutions with varying amounts of CO2 due to varying amounts of  Sodium Hydrogen Carbonate (NaHCO3) and observing the number of bubbles of oxygen that are released as a bi-product of photosynthesis

Hypothesis:  As the concentration of CO2 increases the rate of photosynthesis will increase, until a certain point where the rate of photosynthesis will become constant because of other limiting factors on photosynthesis.  The equation for photosynthesis is – 6H2O +6CO2 → C6H12O6 + 6O2

      Water + carbon dioxide → glucose + water

As carbon dioxide increases in an environment with an adequate water supply photosynthesis should increase so more oxygen will be produced; eventually the rate of photosynthesis will be limited by aspects such as temperature and amount of light present.


Independent Variables:

  • Amount of CO2 in water due to concentration of NaHCO3 placed in water

Dependent Variables:

  • The number of bubbles which rise from Elodea plant in 10 minutes

Constant Variables:

  • Time in which experiment is rate of photosynthesis is observed (10 minutes)
  • Light Source (colour, intensity, distance from plants)
  • Size of Elodea
  • Method of Measurement
  • Temperature
  • Equipment in Experiment
  • Amount of Carbon solution placed in solution
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  • Pencil
  • Pen
  • Paper
  • Stopwatch
  • 5 Beakers
  • 10 test tubes (five for solutions, 5 for funnel)
  • Elodea plant
  • Water
  • Varying percentage of carbon solution (0.1%, 0.2%, 0.3%, 0.4%)
  • 2 lights
  • 2 funnels
  • Accurate scale
  • Tiny spoon
  • Test tube rack


  1. The Elodea plant was cut into 5 equal pieces
  2. Each piece of Elodea was placed in a beaker that had been filled with water  (there were 5  500ml beakers each with water and Elodea)
  3. The 10 test tubes were each filled with water
  4. 1 gram of each NaHCO3 solution was weighed out ...

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