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Photosynthesis Investigation.

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Introduction

Photosynthesis Investigation Analysis Below is the data table showing my results from the investigation, I have also added an adjoining column and calculated the mean average (total of items ( number of items) of the five trials at each level of light intensity: I believe that there are a few anomalous results in the above table and I have decided not to include them in my experiment as I believe they are inaccurate and might distort my conclusion. In the table below I have highlighted any anomalous data that I will remove. I have also drawn a graph of the averages, calculated above, to assist me in identifying inaccurate data. Any anomalous data I successfully identified, by studying the table of results and by observing irregularities in the trend of my averages on the graph, has been omitted and not included in calculating my new averages. I have decided to plot the light intensity (%) against the volume of the gas (mainly oxygen) bubble produced per 10mins per 10g of Elodea (mm�). In order to work out the volume of the gas bubble I will use the formula: V = ? r� x l V = volume of gas (mainly oxygen) bubble (mm�) r = the radius of the capillary tube, 0.5mm l = the length of the bubble (mm) Below is a table containing the new, more accurate averages of the gas bubble length and the gas bubble volumes. Graph (see attached sheet) ...read more.

Middle

I think that the water temperature increased due to heat energy produced by the light source, in this case the bench lamp. Below is a graph briefly indicating the affect the alteration of temperature has on the gas bubble volume. I believe that because enzymes control photosynthesis reactions, the temperature affects the rate of photosynthesis. As the light intensity increases and subsequently the temperature, the rate of photosynthesis also increases. This is because the reactant particles have a higher level of kinetic energy and therefore there are more collisions per second. Below I have drawn two diagrams clearly illustrating how an increase in temperature increases the rate of photosynthesis: I also think that the concentration of carbon dioxide could have affected my results and might be the answer to the fluctuation in my results. The solution that the Elodea was submerged in was enriched with sodium hydrogen carbonate (NaHCO3), 0.3%. This compound increases the availability of carbon dioxide. I believe that it is possible that nearing the end of my investigation there was a reduction in the concentration of this compound, decreasing the availability of carbon dioxide. I also believe that the amount of carbon dioxide present in the water would be reduced, as the Elodea would be absorbing it. Below is a graph depicting the affect of a reduction in the concentration of NaHCO3 has on the gas bubble volume, as well as the rate of photosynthesis: Below I have drawn two diagrams clearly ...read more.

Conclusion

The formula I used to calculate the volume of the gas bubble could be improved. I used a formula typical for calculating the volume of a cylinder, whereas the gas bubble is in fact rounded at each end, meaning the volume is actually smaller then the figures I calculated. However, I think that this is somewhat irrelevant, as the formula provided me with adequate volumes with I was able to plot against the levels light intensity, giving me a rough indication of the rate of photosynthesis, if not an entirely precise one. I believe that five trials were sufficient and I do not think that by increasing the number of experiments would significantly change the accuracy of the results. If I were repeating this experiment, I would like to investigate the relationship between low light levels and the rate of photosynthesis. I believe that there are additional investigations I could conduct to provide supplementary evidence supporting theories regarding the rate of photosynthesis. I would like to investigate the relationship between the wavelength of light and the rate of photosynthesis. I would use the same method but keep the light intensity constant and instead, place a blue, green or red coloured translucent filter in front of the bench lamp. I would plot the various coloured filters against the number of gas bubbles produced, as well as their volume. By using a computer simulation programme, "Multimedia Science School", I have discovered the following: I would like to investigate this further, see whether it is correct and calculate the percentage of difference between each colour of light. ...read more.

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