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affect of light intensity on rate of photosynthesis

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Biology experiment: photosynthesis The effect of light intensity on Inelodea's rate of photosynthesis Aim: Investigating the effect of increasing light intensity on rate of photosynthesis of Inelodea (water plant) Light intensity is manipulated by changing the distance of the beakers from the lamp Rate of photosynthesis is measured by looking at the pH change of NahCO3 solution. CO2 makes water more acidic. As CO2 is gradually used up during photosynthesis, the change in pH of the solution per time implicates the rate of photosynthesis. Hypothesis: The increase of light intensity will increase the rate of photosynthesis of Inelodea Apparatus: * 5g of NaHCO3 (powder) * 5 beakers (100 ml) * Stirring rod * Balance * Universal pH indicators * 5 Inelodea plants (7 Cm long) * Distilled water * Lamp * 1 metre long ruler * Stop watch Method: 1) Fill each of the 5 beakers with 75 ml of distilled water 2) Dissolve 1g of NaHCO3 (use balance to weight NaHCO3) ...read more.


So all have the same characteristics * All plants have same length ensured by Cm ruler * Distance from is lamp was kept accurate by the 1 metre ruler * The time was kept accurate by stop watch * Different plants are used every new experiment so all of them have the same start for photosynthesis Results: Table 0 pH Before the experiment Beaker A Beaker B Beaker C Beaker D Beaker D pH 9 pH 9 pH 9 pH 9 pH 9 Table 0 shows the pH level of each 5 beakers before the experiment Table 1 20 cm from the lamp Time (min) 2 4 6 8 pH 11 12 13 13 Table 1 shows the pH taken from beaker A, which was at 20 Cm distance from the lamp at the time interval 2, 4, 6 and 8 minutes. Graph 1 Graph 1 shows the result from table 1 on graph Table 2 40 cm from the lamp Time (min) ...read more.


The controlled shows no increase in pH. This suggests that there is no other extraneous variable that affect the rate of photosynthesis except light. The graphs shows that it takes longer for the beakers from further off the lamp beakers to have a pH change. For instance graph 3 shows beaker at 60 Cm from the lamp (low light intensity) have only increase 1 pH (from 10 to 11) in 6 minutes (from 2 minutes till 8 minutes). Graph 1 at the same time interval has increase 2 pH (from 11 to 13). This result supports the hypothesis as light intensity increases, rate of photosynthesis also increases. Evaluation: The experiment was success. There is no anomaly in the result. Extraneous variables was minimised by strict controls and careful planning. However the result would be more accurate if instead of using pH universal indicator, a digital pH measuring indicator should be used because it was very hard to identify the colour as well as the pH from the universal indicator. This caused a lot of disagreement during the experiment between my partner and wasted time. ?? ?? ?? ?? Alex Tran ...read more.

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