Core Practical: Effect Of Light Intensity On Photosynthesis Flashcards
Which indicator is used in the CP?
H2CO3 - hydrogen carbonate indicator
What is the method for the light intensity core practical?
1) Prepare different clear glass bottles with 20 algae balls each
2) Add the same amount of indicator to each bottle and put the lid on
3) Place each bottles in equal intervals away from a lamp (eg: 20cm, 40cm, 60cm etc)
4) Compare colour to find pH at start with the colour chart
5) Set up a water tank between the lamp and area where the tubes are.
6) Cover one in foil (so it’s in the dark)
7) Turn on the lamp until you can see obvious changes in the colours
8) Work out the pH at the end (compare colour to chart)
9) Calculate change in pH/hour (end - start)
10) Plot a suitable graph to show the change in pH/hour and distance
How does the colour of the indicator change further away from the lamp in the light intensity core practical?
Orange and Yellow = high CO2 levels - closer to lamp
Red in atmospheric air
Red to magenta to deep purple as CO2 is removed
Change in pH/hour is the measure of the rate of ______
Photosynthesis
What is the dependent variable in this light intensity experiment?
Change in pH/hour
What is the independent variable in this light intensity experiment?
The distance from the lamp (cm)
What colour would the indicator in the foil wrapped tube change to?
It would remain yellow because even though photosynthesis isn’t occurring, respiration is releasing high levels of CO2.
In what way is the rate of photosynthesis proportional to light inetnitsy?
Directly proportional
This is because: one increases, the other increases
More sunlight = more energy to convert reactants of photosynthesis into products
In what way is the distance from light source proportional to the rate of photosynthesis?
Indirectly proportional (1/d^2) The further away from light source = less energy for photosynthesis
