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# In this experiment we are going to investigate if increased light intensity will increase the rate of photosynthesis in the water plant Elodea. We will monitor the rate by counting the number of bubbles of oxygen formed

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Introduction

Name: Laura Akinyi Class: IB1 Subject: Biology Collaborator: Intisar Ahmed and Timmoi Lawoko Date of performance: 2 December 08 The Effect of light intensity on the rate of photosynthesis Introduction Light intensity is one of the three factors that can determine the rate of photosynthesis. Changing the level of this changes the rate of photosynthesis. In this experiment we are going to investigate if increased light intensity will increase the rate of photosynthesis in the water plant Elodea. We will monitor the rate by counting the number of bubbles of oxygen formed or by measuring the volume of oxygen gas formed. We hypothesized that the shorter the distance (independent variable) is between the light source and the plant the more the bubbles (dependent variable) will be formed. Material See instruction sheet. Method 1. Add a spoon of sodium hydrogen carbonate to water in a container and mix. ...read more.

Middle

Place the lamp closer to the plant and measure the distance. Results The number and volume of bubbles formed at different distances from the light source Distance the light source (cm) Temperature before the test Temperature during the test Number of bubbles produced during ten minutes� 1 The volume of the gas formed during ten minutes in cm 1. 47cm 22�C 23�C 148 � 1 0.125 cm 2. 40cm 22�C 21�C 153 � 1 0.125 cm 3. 33cm 20�C 22�C 262 � 1 0.25 cm 4. 24cm 21�C 21�C 266 � 1 0.25 cm 5. 8cm 20�C 20�C 262 � 1 0.25 cm We found that the closer the elodea plant got closer to the light source the more bubbles were formed. However the nearest distance (8 cm) from the elodea plant to the source of light produced less bubbles than the second distance (24cm) thus our experiment supported the prediction to a certain extent. ...read more.

Conclusion

All the carbon dioxide was used up. The temperature was not kept constant. The different trials had different temperatures this was a systematic error since temperature also affects the rate of photosynthesis. Random errors like counting the bubbles inaccurately might have also led to the imprecision. Evaluation The design and method of this investigation was not accurate since some variable such as carbon dioxide and temperature were not kept constant. The weaknesses such as measuring the light intensity by calibrating the distance was not reliable, we should have used a better equipment or method to measure light intensity like using a reliable equipment e.g. a lux meter. We should also wait for a while in each experiment before staring to count the bubbles so that the plant may adjust to the new conditions. To reduce systematic errors we should keep the other variables that affect the experiment like carbon dioxide and temperature constant. We could do this ...read more.

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