IB Biology HL IA - Research Question How is the rate of...

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Research Question: How is the rate of photosynthesis affected by light intensity and sodium bicarbonate ( NaHCO 3 ) in spinach leaves?
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Hypothesis: If the leaf is exposed to higher intensity of light in the presence of a carbon source, then it takes less time for the leaf disks to float to the surface of the solution due to an increased rate of O 2 production through photosynthesis. 2
Variables Control Variables Size of the leaf discs Leaf disks are cut using a hole punch. Type of Spinach The species of the spinach is S. oleracea. Presence of CO2 Existence of bicarbonate in the solution- 6g of bicarbonate is measured with a 6±0.01g balance Temperature The experiment is performed at the room temperature. Volume of the solution The volume of the solution is sucked by syringe which reads 3cc. Independent Variables Intensity of light Existence of bicarbonate in the solution- 6g of bicarbonate is measured with a 6±0.01g balance Dependent Variables Time taken by leaf disks to float The time it takes for the disks to float to the top is kept by a standard stopwatch, and recorded every minute with an uncertainty of ±0.1s 3
Material (for each trial): No. Apparatus Quantity Concentration Uncertainty 1 Sodium Bicarbonate (baking soda) 6g ±0.02 2 Liquid Soap 5mL ±0.1 3 Plastic Syringe 1 4 Plastic Cups 4 5 Spinach Leaves 170g 6 Hole Punch 1 7 Stop Watch 1 ±0.1 8 Beakers 2 500mL 9 Plastic Pipette 2 2mL 10 Ruler 1 30cm ±0.1 11 Stirring Rod 2 12 Microscope Bulb 1 15w 13 Iron Stand 1 14 Weighing Machine 1

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