RP: Photosynthesis (B.6)(B.46)

• what is the independent variable?

  Distance from the light source (light intensity)
• What is the dependent variable ?

  number of bubbles per minute
• 3 control variables

  1)Temperature of the water 2)Carbon dioxide concentration 3)Colour of the light
• how is the rate of photosynthesis measured ?

  rate = total O2 produced/ time
• how is the volume of oxygen measured?

  counting the number of bubbles per minute
• how is the light intensity changed?

  changing the distance if the breaker from the light
• name one random error

  counting the bubbles incorrectly
• give one way to make the results more accurate?

  increase the amount of time you count the bubbles for
• how is the concentration of carbon dioxide controlled ?

  Adding sodium hydrogen carbonate to the solution
• give an alternative way to measure the volume of gas produced?

  Volume of water displaced from a measuring cylinder
• name one risk and precaution

  the lamp may be hot so do not touch
• how is the temperature controlled?

  Water bath
• how is pondweed controlled?

  same species, same age and same length
• what results should you see?

  As the light intensity increases, the rate photosynthesis increases
• what are possible variations on this method ?

  1)Investigate the effect of different coloured lights 2)Investigate the effect of temperature 3)investigate the effect of CO2 concentration