List the materials used in the demonstration. 2. Describe how the liquid solution is made. Include measurements. 3. When she first draws water into the syringe, the leaf discs are floating. Explain why they are floating.

Answer 1

1. Materials Used in the Demonstration:

   • Leaf discs (commonly from a plant like spinach or elodea)
   • Syringe (usually 10 mL)
   • Water (distilled or tap)
   • Baking soda (sodium bicarbonate)
   • Light source (like a lamp)
   • Petri dish or another clear container
   • Optional: Timer or stopwatch

2. Description of How the Liquid Solution is Made:

   • Measurements:
     • Start by preparing a sodium bicarbonate solution. Typically, you can mix about 1/8 teaspoon (approx. 0.5 grams) of baking soda with 200 mL of water. This creates a bicarbonate solution that provides a source of carbon dioxide for the leaf discs.
     • Stir the baking soda in the water until it is fully dissolved.
     • Use this solution for the experiment when filling the syringe with the leaf discs.

3. Explanation of Why the Leaf Discs are Floating:

   • When the leaf discs are first placed in the syringe and filled with water, they may float due to the air trapped in the intercellular spaces within the leaf tissues. Leaves generally have small air pockets that help them maintain buoyancy.
   • The floating occurs because the density of the discs is less than that of the surrounding water. When the discs are submerged in water and not yet saturated with the liquid (pulled into the syringe process, which helps remove some of the air), they can initially float until the air is removed from the tissues, causing them to sink as they become denser than the water.

This setup is commonly used in photosynthesis experiments, and observing the leaf discs can help illustrate the process of oxygen production and the effects of light and carbon dioxide availability on photosynthesis.