REQUIRED PRATICALS

Question 1

What is the process for light intensity and photosynthesis RP6?

Answer 1

1. Start by putting a boiling tube and placing it 10cm away from an LED light source (LED light source is used because they don’t emit that much heat (too much heat would change the temperature of the experiment))
2. Now fill the boiling tube with sodium hydrogen carbonate solution (this solution releases carbon which is needed for photosynthesis)
3. Put pondweed into the the boiling tube with the cut end of at the top. We then leave this for 5 minutes to acclimatise to the conditions in the boiling tube. We should see bubbles of oxygen being produced from the cut end of the pondweed
4. Once we see the bubbles start a stopwatch and count the number of bubbles produced in one minute
5. Repeat this 2 times and calculate the mean number of bubbles produced in one minute
6. Do the WHOLE EXPERIMENT again but start at 20 cm. Then 30cm. Then 40cm.

Question 2

What are the 2 main problems from the practical 6 light intensity and photosynthesis and how can we solve them?

Answer 2

The number of bubbles can be too fast to count accurately
The bubbles are not always the same size. A large bubble would count as a small bubble.

we can solve them by placing the pond-weed under a funnel and catch the bubbles in a measuring cylinder filled with water. We then use the measuring cylinder to measure the volume of gas produced

Question 3

What can we see on the graph/results of RP6 light intensity and photosynthesis??

Answer 3

If we double the distance then the number of bubbles produced per minute falls by a factor of 4. (Inverse square law)