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To find if light intensity affects the rate of photosynthesis.

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Coursework: To find if light intensity affects the rate of photosynthesis Aim The aim of this experiment is to determine whether light affects the rate in which a plant photosynthesises. Equipment * A piece of Canadian pondweed * Stop watch * Basin filled with luke warm water * Power pack * Beaker * Lamp * Gas collecting tube * Funnel * Sodium hydrogen carbonate * Spatula * Transparent bowl * Tweezers Method 1. Firstly I am going to gather my equipment together. 2. I will then plug the power pack into the socket, and then plug the lamp into the power pack. 3. I will then choose a piece of pondweed and trim it to 7 cm (also trimming is important as to renew the plant in a sense). 4. I will then, using my tweezers push the pondweed through the large entry of the funnel letting it slightly making its way into the spout. 5. I will then take this plant holding funnel and place it in the bowl wide entry down. 6. I will then go to the basin with water and put it under the water on its side ensuring that the bowl and funnel are still being held together someone will then come and move a test tube under the water onto the spout of the funnel and with one movement will take the whole thing out. ...read more.


Time I will use the same amount of time each time (1min) to count how many bubbles form. The plant inside This isn't something that we can alter however it is still a variable. The amount of chloroplasts would in increases the rate of photosynthesis the more chloroplasts the more photosynthesis carried out, as chloroplasts contain chlorophyll a substance that traps light energy that is essential for photosynthesis. Distance of the plant from the light source (light intensity) I will make sure that the lamp is the same distance away from the plant throughout the experiment (about15cm away). Diagram of equipment Prediction I predict that the the higher the voltage the more bubbles released. I say this because higher voltage means more light intensity and the more light there is the more the plant can photosynthesise. The rate of photosynthesis to the light intensity is inversely proportional When the lamp is at its brightest it will give more light (energy) that the pondweed will need to photosynthesise at its optimum speed. Also the rate of photosynthesis will increase when light intensity is increased because the amount of energy absorbed by the chlorophyll increases, which makes the transfer of carbon dioxide into sugars also increase. The rate of oxygen also increases when the light intensity increases thus proving how the rate of photosynthesis increases when light does as oxygen is a product of it and the more produced, shows that more photosynthesis occurred. ...read more.


The light energy did not spread out as much as a plain light bulb with no cover or normal sunlight. This distribution of the light energy was more concentrated, probably changing the gradient of the graph. Evaluation Overall, I would state the experiment as a success since my predictions were supported by my results. I feel I could have improved the experiment by repeating it in order to gain accurate results My results however couldn't have been very accurate because the classroom that we worked in was a poor site for carrying out this experiment, we were working very close to a large window and on a bright day, the lights were switched on, and also there were other experiments (the same) going On in the same room this would change the concentration of oxygen and carbon-dioxide in the air. I would improve the experiment by turning off all the lights in the science lab so that the light intensity would be equal for every repeat. I would also control the amount of carbon dioxide in the water by preparing the solution pre hand in order to give the basin a proper mix. To improve the experiment further I would have used a different type of light than the type we use (normal light), I would have used Blue light, and this light is easily absorbed by chlorophyll, and is the same type of light, which comes from the sun. . Saher Rashid 11M6 ...read more.

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