======Bubbling Plants: Quantifying Photosynthesis======


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**Alternative titles:** Light Intensity and Photosynthesis with Elodea
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====Summary====                   
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====Procedure====  
  -Fill a 500 mL beaker with aged tap water and dissolve a small pinch of baking soda; stir until clear.
  -Arrange 18–24 inches of Elodea so leaves are exposed (loop around the beaker bottom); tie loosely and weight so it stays submerged about 1–2 inches.
  -Set the beaker in dim classroom light; start a 5 minute timer.
  -Two observers watch for rising bubbles while a recorder tallies each bubble that reaches the surface.
  -After 5 minutes, position a desk lamp a few inches above the beaker to provide bright, direct light.
  -Reset the timer and count bubbles again for 5 minutes under high light.
  -Record both counts, then compare results across groups; compute mean or median if pooling class data.
  -Make a simple bar graph showing bubble counts for low versus high light and interpret which condition had more photosynthesis.



====Links==== 
Bubbling Plants Experiment to Quantify Photosynthesis - TeachEngineering: 
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Photosynthesis in Elodea - John Hindmarsh: 
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📄 Bubbling Plants Experiment to Quantify Photosynthesis - ncwit.org: [https://www.teachengineering.org/activities/view/duk_photo_mary_act]]\\

====Variations====
  *Test different distances from the lamp to change light intensity.
  *Cover the beaker with colored film (red, blue, green) to compare light colors.
  *Add more or less baking soda to see if carbon dioxide availability matters.



====Safety Precautions====
  *Keep hot bulbs several inches from plastic and plants.
  *Handle glassware carefully on a stable surface to avoid spills and breaks.
  *Do not ingest any materials; wash hands after the activity.
  *Supervise electrical cords and water to prevent shock hazards; keep plugs and outlets dry.




====Questions to Consider====
  *Why do bubbles indicate photosynthesis? (They are mostly oxygen released during photosynthesis.)
  *Why add baking soda to the water? (It supplies dissolved carbon dioxide for photosynthesis.)
  *How should bubble counts change with more light? (Counts usually increase because light powers the reactions.)
  *What is a fair test when comparing low and high light? (Keep all other variables the same: plant amount, water, time, and distance except for the light condition.)
  *Is bubble counting a direct or indirect measure of photosynthesis? (Indirect; it infers photosynthesis rate from visible gas production.)