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Elodea experiment

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Introduction

Elodea experiment Aim To find out if temperature affects the rate of photosynthesis in elodea. Apparatus Heat mat, gauze, Bunsen burner, tripod, beaker, thermometer, funnel, goggles, test tube, water, elodea, sodium hydrogen carbonate, lamp, spatula. Plan Put the elodea in a beaker full of water the snap the end that is growing off to get rid of any air bubbles. Turn a funnel upside down then place it over the elodea and top up the beaker so that the top of the funnel is covered. Then fill a test tube with water and place thumb over the top, turn the test tube upside down and put in under water then take your thumb off. The water should not escape because it is underwater. Move the top of the test tube across and put over the top of the funnel. Empty some water so that it does not spill. The test tube full of water is there so that you can see the air bubbles produced during photosynthesis. Add a thermometer and record the temperature as your starting temperature. Now count how many bubbles travel up the test tube in 5 minutes, so that you can have a control. ...read more.

Middle

Ensure that the bubbles are counted in the same way for all of the readings and repeat these steps for 15 c 20 c 25 c 30 c 35 c above the starting temp and record the results for all of them. With your results divide the number of bubbles in 5 minutes by 5 so that you have the average rate of photosynthesis per minute. Record these results onto a graph with the temperature along the y-axis and the rate of photosynthesis along the x-axis. Prediction I predict that the elodea will photosynthesise greatest at around 30 c because this is the optimum temperature for enzymes and I think this will be reflected in the enzymes that do photosynthesis. However I think that at about 50 c the elodea will no long photosynthesise because the heat will denature the enzymes, there for the graphs to show my results will have an "n" shaped curve. I think this will happen because at lower temperatures than 30 c the enzymes will not work as well and so photosynthesise slower, but do not denature. The only limiting factor is temperature because we have constant light supply from the lamp and plenty of carbon dioxide from the sodium hydrogen carbonate. ...read more.

Conclusion

Also the heat may not have been evenly distributed throughout the water so some parts of the elodea may have been hotter than other areas. Also the temperature fluctuated while I was counting the number of bubbles, sometimes being higher than the temperature I was aiming for, and sometimes being lower. When I was counting the bubbles, they were different sizes that meant that if a large bubble were produced it would contain more carbon dioxide, and would mean more photosynthesis would have been done. I only counted large bubbles as one bubble, and small bubbles also as one bubble, which meant that the actual rate of photosynthesis was not accurately recorded. This would mean that the results are inaccurate and are therefore only be an estimate. The graph reflects the "n" shape that I predicted in my prediction. In my prediction I thought that the optimum temperature would be around 30 c but in fact it was twice as much. If I were to repeat this experiment I would like to be able to heat the water more accurately to ensure that the heat was distributed evenly. I would also try and find a more effective method of counting the bubbles, because at high temperatures it was difficult to count all the bubbles. ...read more.

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