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# An investigation into the effect of light intensity on the rate of photosynthesis on Canadian pondweed.

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Introduction

An Investigation into the Effect of Light Intensity on the Rate of Photosynthesis on Canadian Pondweed Background Information: Photosynthesis is an organic chemical reaction which green plants use to produce glucose from carbon dioxide and water. Its equation is 6CO[2] + 6H[2]0 C[6]H[12]O[6] + 6O[2] However, carbon dioxide and water cannot react on their own "They have to be given energy to make them combine. The energy which green plants use for this is sunlight energy". We can determine that if sunlight gives the reaction energy, and increase in the intensity of the sunlight will give the reaction more energy, which will speed the reaction up. We can therefore safely predict that as the intensity of the light increases, so too will the speed of the reaction. List of Key Variables: The key variables that could affect my experiment are the temperature at which the water is, a thermometer will be used and if the temperature rises or falls we will need to restart because this could affect the whole experiment. ...read more.

Middle

Prediction and Hypothesis: In this experiment we will be investigating whether or not the light intensity will change the rate of photosynthesis in Canadian pondweed. We will be doing this by seeing the rate at which oxygen bubbles are produced, because when photosynthesizing the Canadian pondweed produces bubbles and we can see the rate of bubbles against light intensity. The further the light away from the pondweed the less the light intensity, so the less the amount of bubbles produced, as shown in the graph below. I think if I double the distance the light is away from the pondweed. Then the rate at which the bubbles are produced will half because they are directly proportional to each other because the pondweed produces the bubbles when it is photosynthesizing it produces oxygen bubbles so the light = bubbles so the less the amount of light the less the amount of bubbles. BUBBLE RATE LAMP DISTANCE AWAY FROM PONDWEED [image003.gif] BUBBLE RATE [image005.gif] LIGHT INTENSITY Observations: We will be observing how many bubbles are produced against the light intensity then recording the results onto a table. ...read more.

Conclusion

Set up apparatus as above. 2) Fill the test-tube with pond water, and then in the large beaker of cold water. 3) Insert a thermometer into the beaker, and record the temperature at the beginning and end of each experiment, merely as a precaution against a significant rise in temperature, which is not expected. 4) Set up a lamp at a set distance from the plant, ensuring that this distance is from the filament of the lamp to the actual pondweed, rather than the edge of the beaker. 5) The light intensity was measured in the same way as described in the preliminary experiment, and assumed to be the same at any point at any particular distance. 6) When bubbles are being produced at a steady rate, clear any previous bubbles from the tubing by moving the syringe. 7) Start the stopwatch, and wait for 1 minute. 8) Move the bubbles, which have been collected at the bend in the tubing to the part of the tube with a scale. ...read more.

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