To investigate the affect of light intensity on oxygen produced by pondweed.

Apparatus

A lamp

2xBeakers or jam jars

Spatula

Sodium hydrogen carbonate

Paper clip

2cm of pondweed

Stop watch

Plan

.Cut off a sprig of pondweed 5cm long.

2.Attach a paper clip to the top end to weigh it down.

3.Put it in a beaker or jam jar water level should be 2cm over pond weed.

4.Add a spatula of sodium hydrogen carbonate to the water this will ensure that the pondweed has a good supply of carbon dioxide.

5. Place a lamp to one side of the beaker or jam jar.

7.Now put the lamp 50cm away from the beaker then 40cm, 30cm, 20cm and 10cm, wait a few minutes, then count the number of the bubbles again. Do this three times and work out the average for each distance for one whole minute.

Diagram

The length of the test will be in one minute intervals.

Distance (cm)

Test One

Test Two

Test Three

Average

of pond weed away from lamp

(In Bubbles)

(In Bubbles)

(In Bubbles)

(In Bubbles)

50cm

57

57

50

54

40cm

85

73

76

78

30cm

46

44

49

46

20cm

25

22

26

24

0cm

7

8

20

8

Analysis

I have found out the nearer the lamp to the beaker filled with the water and a piece of pondweed the more bubbles are produced

So as I move the lamp away the number of bubbles goes down

At the start of the graph when the lamp was closest the number of bubbles dropped a large amount then the drop got smaller and smaller and levelled off.

Evaluation

I think the test was in accurate because the size of the bubbles could have changed so it could have produced a bigger or smaller bubble.

Th e way to make it a fair test is measuring the volume of the bubbles.

Jason kench 10F2

Mrs Roberts