Photosynthesis: How do plants get energy?

In this lab, students explore the process of photosynthesis in spinach leaves. As oxygen is produced, the density of the leaves change and they will begin floating in a sodium bicarbonate solution. The time it takes for a certain number of leaves to float can be used to calculate the rate of photosynthesis.

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Recommended Prerequisites:
  • none!
Key Concepts:
  • Photosynthesis is the primary means by which plants get their energy. They derive this energy from a sugar called glucose (C6H12O6).
  • To make glucose, sunlight is captured in pigments like chlorophyll, the substance that gives leaves their green color.
  • The sun’s energy is passed through a chain of events that breaks water (H2O) into oxygen (O2) and creates a store of energy-rich molecules. These molecules will enter a continuous cycle of events to build glucose out of carbon dioxide (CO2 ) from the air.
  • 1 8 oz. box baking soda
  • 1 L water
  • Teaspoon
  • Graduated beaker (200mL)
  • 5 transparent cups
  • single hole punch
  • 7 fresh spinach leaves
  • Small bottle of dish soap, clear (if available)
  • 1 large desk lamp ( >60 watt bright white, if possible)
  • 2 sheets of cellophane: one green, one red (transparencies colored with markers work)
  • 4 plastic syringes (10 mL)
  • ruler
  • 2 shoe boxes, pre-cut according to pre-lab directions
  • 2 pieces of cardstock or heavy paper, pre-cut according to pre-lab directions
  • 1 L graduated beaker
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