Required Practical 6: Photosynthesis Flashcards
1
Q
What is the first step of the practical?
A
- Start by taking a boiling tube and placing 10cm away from an LED source
- Too much heat would change the temperature of the experiment
2
Q
What is the second stage of the practical?
A
- Fill the boiling tube with sodium hydrogen carbonate solution
- Sodium hydrogen carbonate solution releases CO2, which is needed for photosynthesis
3
Q
What is the third step of the practical?
A
- Put a piece of pondweed into the boiling tube with the cut end at the top
- Leave this for 5 minutes to acclimatise to the conditions in the boiling tube
4
Q
How will we know when the reaction has occurred?
A
- We should see bubbles of gas being produced from the cut end of the pondweed
- This gas is oxygen and that is produced by photosynthesis
5
Q
What is the fourth step of the practical?
A
- Start a stopwatch and count the number of bubbles produced in 1 minute
- Repeat this 2 more times and calculate the mean number of bubbles produced in one minute
6
Q
What is the fifth step of the practical?
A
- Do the whole experiment again from the start at 20cm, then 30cm, then 40cm
7
Q
What are the problems with this reaction?
A
- The number of bubbles that can be too fast to count accurately
- The bubbles are not always the same size. A large bubble would count the same as a small bubble
8
Q
How could we improve this experiment?
A
- Place the pondweed under a funnel and catch the bubbles in a measuring cylinder
- The use the measuring cylinder to measure the volume of oxygen produced
9
Q
What result should we get from this experiment?
A
- If we double the distance, then the number of bubbles per minute falls by a factor of four.
- If we double the distance, the light intensity falls by four times
10
Q
When light intensity falls, what happens to the number of oxygen bubbles?
A
- Because we need light for photosynthesis, that also causes the number of oxygen bubbles to fall by four times.
