Science fair project


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Science fair project

  1. 1. Science Fair Project How Does pH Level Affect Overall Light Absorption of Plant Leaves Stuart Klein Eric Dybas Spanish River Community High School
  2. 2. Statement of the Problem <ul><li>Does pH has any direct influence on the ability of plant leaves to absorb ultraviolet rays. </li></ul>
  3. 3. Project Overview <ul><li>Water three Spider plants with water at a pH of 3, three with a pH of 7, and three with a pH 10 over a three week period. Then measure light absorption using a UV Spectrophotometer. </li></ul>
  4. 4. Research <ul><ul><li>Looked up which plants would show significant growth over a 3 week period </li></ul></ul><ul><ul><li>Checked that chemical room contained enough NaOH, HCl, and distilled water to complete project </li></ul></ul><ul><ul><li>Made sure that lab equipment (UV Spec, cuvettes, pH probe, and mortar and pestle) were easily accessible </li></ul></ul>
  5. 5. Variables <ul><li>Dependent Variable: Amount of absorption of light by leaf paste in nm. </li></ul><ul><li>Control: Plants watered in pH of 7 </li></ul><ul><li>Independent Variable: Manipulation of pH level of tap water using NaOH and HCl. ranging from acidic to neutral to basic </li></ul>
  6. 6. Hypothesis <ul><li>If spider plants are watered using more acidic water, at a pH of 3, then their leaves will absorb less light than plants watered with more basic water, at a pH of 10. </li></ul>
  7. 7. Materials <ul><ul><li>9 Spider plants </li></ul></ul><ul><ul><li>Between 1-2mL of HCl and NaOH per watering </li></ul></ul><ul><ul><li>48mL distilled water per watering </li></ul></ul><ul><ul><li>UV Spectrophotometer </li></ul></ul><ul><ul><li>10 cuvettes </li></ul></ul><ul><ul><li>4mL distilled water per cuvette </li></ul></ul><ul><ul><li>pH probe </li></ul></ul><ul><ul><li>Miracle grow </li></ul></ul><ul><ul><li>Mortar and Pestle </li></ul></ul><ul><ul><li>Safety goggles </li></ul></ul><ul><ul><li>Lab gloves </li></ul></ul>
  8. 8. Procedure <ul><li>Purchase 9 spider plants. </li></ul><ul><li>Plant spider plants in three rows of three at my house in miracle grow. </li></ul><ul><li>Using 48mL of distilled water and a pH probe, add various amounts of NaOH and HCl to change the pH level to either 3 or 10. 50mL of distilled water will be used for the control. </li></ul><ul><li>Every other day, water each plant with approximately 50mL of water of respective pH. </li></ul>
  9. 9. Procedure (continued) <ul><li>After a three week period has elapsed, remove leaf that is most directly in sunlight from each plant. </li></ul><ul><li>Crush up leaf using mortar and pestle. </li></ul><ul><li>Add crushed leaf parts to 4 mL of distilled water </li></ul><ul><li>Prepare a “blank” with 4mL of distilled water and no plant. </li></ul><ul><li>Allow spectrophotometer to warm up for 20 minutes </li></ul><ul><li>Set mode to “transmittance” and wavelength to 400 nm </li></ul><ul><li>Set transmittance to 0% </li></ul><ul><li>Wipe down blank, insert it, and set transmittance to 100% </li></ul><ul><li>Remove blank, wipe down sample being measured, and insert it. </li></ul><ul><li>Change mode to absorbance and record absorbance value in absorbance units. </li></ul><ul><li>Repeat for all 9 plant samples. </li></ul><ul><li>Record data. </li></ul>
  10. 10. Data/Observations
  11. 11. Conclusion <ul><ul><li>Although data indicates slightly that the higher pH results in less sunlight absorbance, further experimentation is required to interpret whether these results are valid. Several experimental factors may have led to these results being inconclusive. Due to the nature of the spider plant, selection of which leaf was most directly in sunlight was difficult to judge. This may have caused the wrong leave to be analyzed. Due to the range of absorbance values allowed by the UV spectrophotometer, one absorbance amount for a plant from pH 3, and pH 7 groups were too high to calculate. Uncertainty of these figures alters final results. Due to need for plants to be exposed to the most sunlight possible, they were also exposed to rain of uniform pH. Despite constant systematic watering with altered pHs, rainwater was more prominent and possibly homogenized results. Ultimately my hypothesis was not supported due to inconclusive results. </li></ul></ul>
  12. 12. Works Cited <ul><li>Altman, John. &quot;Main Site Navigation Protocols.&quot; Emory Microbiology & Immunology . 24 Dec. 2003. Web. 29 Sept. 2010. <>. </li></ul><ul><li>&quot;Light Absorption for Photosynthesis.&quot; Test Page for Apache Installation . Web. 29 Sept. 2010. <>. </li></ul><ul><li>McDarby, Michael. &quot;Biology of Animals & Plants -  Photosynthesis.&quot; FMCC Faculty Server . 2010. Web. 29 Sept. 2010. <>. </li></ul><ul><li>&quot;Spider Plant Care.&quot; Essortment Articles: Free Online Articles on Health, Science, Education & More.. Pagewise, 2002. Web. 29 Sept. 2010. <>. </li></ul><ul><li>&quot;Using the Spectrophotometer.&quot; Welcome to the Ortí Lab . UNL. Web. 29 Sept. 2010. <>. </li></ul>