Investigating Photosyntesis in Pond Weed

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Investigating Photosyntesis in 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:

[IMAGE]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

10

32

29

32

20

30

28

22

30

29

28

13

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

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