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Investigating the factors that will affect the rate of photosynthesis.

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Investigating the factors that will affect the rate of photosynthesis Aim: I will be investigating how light intensity affects the rate of photosynthesis, whether it decreases or increases the rate of photosynthesis. Background Knowledge: Photosynthesis is the process by which plants make their own food. For photosynthesis to occur, plants need: * Light energy from the sun * Chlorophyll to absorb light energy * Carbon dioxide from the atmosphere and from respiration in plant cells * Water which is absorbed by the roots and transported to the leaves by the xylem tubes. Photosynthesis can be summarised by the equation: 6CO2 + 6H2O C6H12O6 + 6O2 The reactants are Carbon dioxide and Water; the products are Glucose and Oxygen. The factors that affect the rate of photosynthesis are: * Light intensity- if the light is brighter, then the rate of photosynthesis increases and visa versa. * Water supply- if a plant cannot absorb enough water, then the rate of photosynthesis decreases. * Carbon dioxide concentration- if the percentage of carbon dioxide in the atmosphere increases, so does the rate of photosynthesis. * Temperature- if the temperature increases, then the rate of photosynthesis also increases, (however, temperatures above 40OC can damage a plant and photosynthesis stops because the chlorophyll gets too hot). ...read more.


8. Boiling tube- This is where I will put the Elodea plant along with some water, so photosynthesis will take place. 9. I will use this because it is one of the reactants of photosynthesis. The measurements I will be taking are: * The amount of water in the boiling tube, in millimetres. * The distance between the Elodea and the lamp, in centimetres (10cm-60cm). * The number of oxygen bubbles produced. * The minutes of each interval for every minute, to about 5-8 minutes. Safety: 1. Do not touch the light bulb as it will be very hot. 2. Keep the lamp and boiling tube away from the edge of the table so it does not fall as smash. 3. Tie back long hair and secure loose jewellery and items of clothing. 4. Do not touch the power supply with wet hands and make sure water is not poured near the power supply. 5. When pouring water, pour it in the sink. 6. Keep eyes on experiment at all times. Method: 1. Set up apparatus as shown below. 2. Measure 10cm between the boiling tube containing the Elodea plant and the lamp. 3. Switch on the lamp and start the stop watch. 4. ...read more.


Evaluation: My method worked very well; there were no results which contradict my background knowledge or prediction. My step-by-step guide was very helpful and my evidence obtaining procedure work well. The quality of my result was quite high because I only had 2 anomalous results which's percentage of errors were not too great but 1 was over 10% and may be considered invalid but apart fro this most of my results are valid. My procedure was very suitable because it did not cause any mistakes which could have caused shock and unexpected results, so it is very suitable. To improve my work I could have repeated the experiment another 4 or 5 times to solidly confirm my conclusion and I could have do my experiments in a close area, where the temperature and carbon dioxide were 100% constant and therefore would not affect my results the slightest bit. Percentage of error= error/what it should be *100 = 0.3/4.2 * 100 = 7.1% This error is not over 10% and is insignificant, my result is therefore still valid. Percentage of error=error/what it should be *100 =0.25/1.25 *100 =20% This percentage is over 10% and can be considered invalid and is probably due to human error such as miscounting of the number of oxygen bubbles. ...read more.

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