The aim of this experiment is to find out what effects the amount of photosynthesis happening in a pond weed.

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Biology Coursework

Photosyntesis in a Pond Weed

Aim:

The aim of this experiment is to find out what effects the amount of photosynthesis happening in a pond weed.

Introduction:

A piece of pondweed will be cut and placed into a test tube containing water and sodium hydrogen carbonate, which is placed inside a beaker containing water. A lamp will be shined on to the pondweed and the amount of bubbles released from the plant will be counted. The lamp will be adjusted to different distances from the plant to try and obtain different results. The amount of bubbles will be counted for a period of one minute. The temperature of the water would be recorded at the start and end of the minute.

Photosynthesis Equation:

6CO2 + 12H2O SUNLIGHT C6H12O6 + 6H2O + 6O2

Preliminary Work:

The problems that arose whilst doing the preliminary experiment was that too much sodium hydrogen carbonate was placed inside of the test tube and all the water had turned cloudy so it was impossible to count the amount of bubbles. Also the beaker was placed too far away from the light which meant that the light wasn't reaching the beaker. The preliminary experiments showed that the closer the light is to the beaker the more bubbles appear.

Distance (cm)

Start Temp (ºC)

End Temp (ºC)

Amount of bubbles in 1 minute

0

32

29

32

20

30

28

22

30

29

28

3

40

29

29

6

50

28

28

2

60

27

28

2

Fair Test:

The experiment will be made fair by adding the same amount of sodium hydrogen carbonate each time so that this will not change the amount of bubbles for the change of distance. Also the same lamp will be used each time so that the same light is reaching the beaker each time. The experiment will take place in the same place each time so that the light coming from outside or the ceiling will be kept the same each time. The same amount of water will be in the beaker and test tube each time. The distance of the light will be changed each time so that results can be made for different lengths. The temperature will be kept roughly the same so that the temperature doesn't affect the amount of bubbles, a thermometer will be used so that the temperature can be seen and judged. The piece of pond weed inside the test tube will be the same throughout the experiment so that the results are all based on the same pond weed. The same person will be counting the bubbles, time, temperature and amount of sodium hydrogen carbonate each time to make it fair.
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Prediction:

I predict that the closer the beaker is to the light the more bubbles will appear, this is because the closer it is the more light can be absorbed by the plant causing more photosynthesis to happen. Also the light may heat up the water which will make the enzymes move more and faster because they have more energy and that will increase the reaction speed. At 100cm there will be the least amount of bubbles and at 0cm there will be the most amounts of bubbles. As more particles are involved then there is more ...

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