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An investigation into how the amount of light affects the rate of photosynthesis

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Introduction

An investigation into how the amount of light affects the rate of photosynthesis We are going to do an experiment on how the rate of photosynthesis is affected by the light intensity. The plant that will be photosynthesising is called elodea. It is a pondweed therefore photosynthesises under water. We will now be able to count the oxygen bubbles or develop a method were we can collect the oxygen given off by the pondweed. Photosynthesis is what keeps a plant alive. The energy for photosynthesis to work comes from the sun the air and the ground. A substance called chlorophyll absorbs the sunlight. Chlorophyll is found in chloroplasts and chloroplasts are mostly found in cells in the palisade layer. Also for photosynthesis to be carried out it needs water and carbon dioxide. The carbon dioxide is dissolved into the water and the pondweed will get water and carbon dioxide through diffusion. The light is than used to make sugar out of carbon dioxide and water. The waste product is oxygen. Here is the equation Sunlight 6CO2 + 6H2O ((((((((( C6H12O6 + 6O2 Carbon dioxide + water Chlorophyll Sugar + Oxygen On are preliminary experiment we tried to measure the volume of oxygen produced but couldn't collect ...read more.

Middle

We did this because we were having trouble getting results and we decided this would increase are chance of getting results. Also instead of adding a spatula of sodium hydrogen carbonate we weighed it and put in 0.1g. We did this because it was a lot fairer as one spatula could vary from another. The boiling tube will be put in a beaker filled with water to keep the temperature constant. We will put a thermometer in the boiling tube to keep the temperature constant. We need to keep the temperature constant because heat affects photosynthesis by speeding up the cellular activity. But if you heat a plant up over 40oC photosynthesis will slow down and the plant will die. Our experiment is to see if the light intensity effects photosynthesis so we need to measure the light intensity to see how much it changed by. We measured the light intensity using a light sensor this went just by the boiling tube. A clamp, attached to a clamp stand, will hold up the light sensor. By doing this will mean I am conducting a fair experiment. Summary of preliminary and final experiments Preliminary experiment Final experiment Pond weed length(cm) ...read more.

Conclusion

intensity 16.9 14.2 9.4 4.8 3.5 2.1 Temp oC 21/21/21 22/22/21 20/20/21 21/20/21 22/23/23 23/22/22 Did it keep constant / / / / / / Graph Prelim Final Why straight line or curve? From looking at my results I can tell that the amount of oxygen given off is affected by the light intensity. The graph shows the amount of bubbles decrease the further away the lamp. As you move the lamp further away the light intensity decrease. Conclusion By looking at my graphs and result tables I have found out that my prediction was right. The closer the lamp is to the pondweed the faster it photosynthesis. Also sciences back my result up because if you look at the formula for photosynthesis. Sunlight 6CO2 + 6H2O ((((((((( C6H12O6 + 6O2 Carbon dioxide + water Chlorophyll Sugar + Oxygen If you increase CO2 or H2O or sunlight it will increase the rate of the reaction but this can only work if there's enough of the other to limiting factor. Also if you decrease anything this will slow down the reaction. But H2O is unlikely to be a limiting factor in are experiment as there is enough water because pondweed is an aquatic plant. ?? ?? ?? ?? ...read more.

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