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Investigate what changes the rate of photosynthesis.

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Investigating the rate of Photosynthesis Aim To investigate what changes the rate of photosynthesis. Variables For the experiment there are two types of variables, them being dependent and independent. The dependant variable is the condition that will be used to experiment with, in this case the light intensity. The independent variables are those that are either kept constant or change. The possible variables for this experiment are: > Distance of the lamp > Power of light (light bulb) > Length of elodea > Amount of water > Size of test tube > Time spent counting If the power or the amount of light varies, this will affect the results as I know from scientific knowledge that the more light there is the higher the rate of photosynthesis will be. The length of the elodea will have a dramatic effect on the results, as I know from a past experiment that the bigger the elodea the higher the rate of photosynthesis will be therefore it is crucial to keep it constant. ...read more.


5) Record your results in an orderly fashion (table). 6) Repeat steps 2-5 but with the tube at 0 cm., then 5 cm., and finally 25 cm, going up in 5 cm each time, from the light. When I change the light intensity, I will count the amount of bubbles, and compare the results to see how they affect the rate of photosynthesis. Light intensity is going to be measured based on the distance the lamp is from the elodea, as the lamp moves further away the light intensity decreases. This is known using the formula, light intensity = 1 d� Preliminary work showed to be of a good use when planning the experiment, as I knew an interval of 5cm between six different distances will give a decent set of results. To enhance the level of accuracy of the results the experiment will be repeated three times. The safety aspect for this experiment is that I need to be cautious while handling water around the lamp, and that no water should be dropped. ...read more.


photosynthesis increased at first in direct proportion, but gradually levelled off and did not show a major increase, although there was an increase. Evaluation The experiment that was conducted worked well and backed the prediction, although there were not many anomalous results, there were some, which are shown in the table of results, highlighted in red. These anomalies could be eliminated, if the experiment was to be repeated in a different way. A better way would be to collect oxygen given off in a burette, over a longer time, i.e. about 5 minutes, with more repeats, and measure the total volume of the oxygen. This was the experiment would exclude anomalies as the measure will be more accurate and reliable, than counting bubbles. Another reason why the results may not have been totally reliable is because when the lamp gave out light it also gave off heat, and this would have also as well as the light intensity increased the rate of photosynthesis. Therefore if the experiment was to be repeated a heat shield should be used, i.e. a tank of water to absorb heat but allow light to pass through. ...read more.

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