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An Investigation Into The Factors Affecting The Rate Of Photosynthesis.

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An Investigation Into The Factors Affecting The Rate Of Photosynthesis Aim The aim of this investigation is to find out which factors determine the rate of photosynthesis in pondweed. Equipment List & Diagram: * Sodium Hydrogen Carbonate * Lamp * Scales * Beaker * Photosynthometer * Water * Spatula * Stop Clock * Pondweed (Elodea) * Retort Stand with Clamp Possible Variables: The key variables that may determine the rate of photosynthesis are: * Light Intensity - The lamp's distance from the beaker containing water shall be varied. * Concentration of CO� - Sodium Hydrogen Carbonate (NaHCO�) shall be added to the H�O in the beaker. Amounts of NaHCO� shall be varied. * Temperature - This is not an option in this investigation because altering the temperature may denature the plant's enzymes, thus killing the pondweed. Measurements: The following measurements will be taken during the experiment: * Amount of NaHCO� (g) * Light Intensity (calculated via the formula 1/d�) * Time Taken (secs/mins) * Amount of O� Given Off By Plant The results of the experiment will be recorded in a simple table. Prediction: I predict that as the amount of NaHCO� increases there will also be an increase in the amount of Oxygen (O�) given off. This is because when the NaHCO� is added, the amount of Carbon Dioxide (CO�) ...read more.


When all of this is set up I can begin taking experimental readings. Using a stopwatch I will time 3 minutes. After 3 minutes is up I shall measure the amount of air bubbles (oxygen) in the photosynthometer. After I have recorded these results I shall pull up the syringe again so it sucks up these air bubbles. I will then repeat this, but now I will add specific amounts of Sodium Hydrogen Carbonate. The specific amounts will be 0.5g, 1g, 1.5g, 2g & 2.5g - all weighed out on scales before being added to the water solution and stirred in with the spatula. To ensure quality results I shall repeat the whole procedure twice, thus I shall carry out the experiment 3 times. After collecting these results I shall calculate averages for each different amount of sodium hydrogen carbonate and present all this in a table. Safe Testing: To ensure that the test it safe I shall only have the lamp switched on whilst readings are being taken during the experiment, so this lowers the risk of someone burning themselves on the bulb. Fair Testing: To ensure that the experiment is fair I shall keep the light intensity the same, so that this does not affect the rate of photosynthesis. ...read more.


Evaluation: Over all I believe that the investigation went to plan and the readings and measurements I took were accurate and consistent. There were no anomalies, from the 3 experiments, which shows that I must have being carrying out the procedure well. The experiment perhaps could have been more accurate if the light intensity had been kept the same, which is hard when working during the day. I believe though that given the circumstances, I kept the light intensity as accurate as possible. Also, the photosynthometer is very small and it is hard to make out the oxygen bubbles with it. If I were to have used a burette I would have been able to spot more oxygen bubbles and therefore take more accurate readings. Also, the gas given off causes the amount of water in the burette to decrease - displacing the water in effect - which makes it easy to measure the amount of gas given off. To extend the investigation I could practise more variables, such as altering the distance of the lamp from the beaker (light intensity) and change the temperature by heating the beaker in which the elodea is in. I could also alter the size/surface area of the pondweed to see if this affects the rate of photosynthesis. ...read more.

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