Planning an experiment to find out if light intensity alters the rate of photosynthesis of a plant.
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Planning an experiment to find out if light intensity alters the rate of photosynthesis of a plant Introduction In this experiment I am trying to find out if light intensity alters the rate of photosynthesis of a plant by using waterweed in different light intensities. I would have to consider rate-limiting factors such as the amount of carbon dioxide in the water. To make sure the carbon dioxide supply does not run out, sodium hydrogen carbonate could be added in the water. A temperature rise may cause photosynthesis to speed up, so in order for this experiment to be a fair test I would need to keep the water at a constant temperature from the beginning of the experiment. I would also need to know if the bubbles of gas produced by the plant is oxygen.
Method I will measure the rate of photosynthesis in this experiment by using waterweed in a waterbath. The waterbath will be set up with approximately 5cm of sodium hydrogen carbonate solution that will help maintain a good supply of carbon dioxide. The water in the waterbath will have been left for a few days in the room the experiment will take place in, as it will therefore be at room temperature and will also be de-chlorinated, making this experiment a fair test by making sure it is at a constant temperature. A waterweed shoot of about 5-10 cm long will be selected. A paperclip will be slid over the tip of the shoot, which will then be dropped into the waterbath, acting as a weight so the shoot is held underwater.
This will be repeated when the lamp is 30 cm away from the waterbath. Now, the bulb in the lamp will be changed to a 150-watt bulb and the experiment will be repeated in the same way so it is a fair test. It will start with a distance of 10cm with a jar over the waterweed to check if the gas given of by the plant is oxygen. Next, will be a distance of 20cm and then 30cm, as before, and each time the rate of bubble production will be noted. So that the results are accurate, the experiment will be repeated three times. So that, overall, the experiment will be fair, the same amount of water and sodium hydrogen carbonate and waterweeds of the same size will be used. For safety measures, we will ensure that the bulbs and the water do not come into contact.
This student written piece of work is one of many that can be found in our GCSE Green Plants as Organisms section.
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