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An Investigation into the Various Factors Affecting Photosynthesis

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An Investigation into the Various Factors Affecting Photosynthesis Aim: The aim of this investigation is to determine the factors that affect the rate of photosynthesis and what affect they have. Introduction: Photosynthesis is a chemical reaction that takes place in green plants. The reaction is endothermic and uses light energy to produce glucose. Green plants feed autotrophically, which means that they use inorganic substances to make organic ones, this is called autotrophic nutrition. The inorganic substances that they use are CO2, H2 O and minerals. Green plants use sunlight to give them energy to combine carbon dioxide with water, which produces glucose. This can be shown as the following word and symbol equations: Sunlight CARBON DIOXIDE + WATER GLUCOSE + OXYGEN Chlorophyll 6CO2 + 6H2O C6H1206 + 6O2 The word photosynthesis means light (photo) manufacture (synthesis). The plants need the suns light energy and so trap it in the chlorophyll, the pigment that makes them green. There are three factors that can limit the rate of reaction in photosynthesis and these are the light intensity, temperature and carbon dioxide levels available. ...read more.


Elodea is used because it is a known photosynthesiser. It also gives off gas bubbles from a specifically cut edge, which can be seen when the plant is submerged in water. Prediction: I predict that as the intensity of light is increased so to is the rate of photosynthesis. The two are directly proportional to one another. This means that the closer the light bulb is to the elodea the more gas bubbles of oxygen there will be given off, and the more energy that is trapped in the chloroplasts, the more energy there will be. Therefore by doubling the light intensity you are doubling the energy released. Light intensity is inversely proportional to the distance squared which can be shown as light intensity = 1/d2 . This is because as the light bulb is moved further away from the elodea, the light energy is dispersed over a larger area and less of it reaches the elodea. The light intensity will only increase the rate of reaction to a certain point because at that point something else will limit it, such as the levels of carbon dioxide or the temperature. ...read more.


It will be checked throughout the experiment with a thermometer. - Water Volume, the water will be measured before the experiment, as long as there is more that 400ml in the beaker and 40ml in the test tube it does not matter what the exact value is. - Carbon Dioxide, sodium hydrogen carbonate will be dissolved into the water in both the beaker and test tube. I will make sure there is always an abundance of CO2 , one spatula should be enough. - Light, the same light bulb will be used throughout the experiment to ensure the light wavelength and intensity of the bulb is always the same. Safety: Although this experiment may not be considered very dangerous, the following precautions should be taken: - Make sure no water comes into contact with the electrical mains. - Be careful when cutting the elodea with the sharp razor blade. - Wash hands before and after handling the elodea and the pondweed. - Do not touch the light bulb. - Be careful when handling glass. Fair Test: To ensure that the experiment is as fair as possible the following rules should be applied: - Keep all the other variables constant apart from light intensity. ...read more.

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