Activity time: 8 minutes

Materials for Activity

• Tray to hold experiment materials
• Wide-top glass jar or large clear plastic cups, one per participant or work group
• Baking soda
• Vinegar
• Two 1/4 cup measuring cups
• Children’s bubble soap with wand, enough for participants to share
• Optional: Two additional trays for materials, if using Station Model
• Optional: Written instructions, if using Station Model

Preparation for Activity

• Gather materials.
• Review directions.
• Prepare trays with materials for experiment.
• Optional: If participants will rotate from experiment to experiment in groups (Station Model), print or write the instructions for this experiment and set at this station.

Description of Activity

Give these instructions while a co-leader or volunteer performs this experiment:

This experiment, inspired by Joseph Priestley’s work, demonstrates that carbon dioxide is heavier than air.

Put 1/2 cup of vinegar in the bottom of a clear, plastic cup. Next, use the bubble wand, and the bubble solution to gently blow some bubbles into the cup, observe what happens. Measure 1/4 cup of baking soda; ready the bubbles and bubble wand. Pour the baking soda into the cup of vinegar and then quickly and gently blow a few bubbles into the cup. What happens to the bubbles now?

What did Priestley realize from this experiment? In an empty container, or on top of water, bubbles will sink because the air within them is the same density as the air that surrounds them. In a container with carbon dioxide, the bubbles will "float" because the denser carbon dioxide sinks to the bottom of the container and pushes the oxygen-rich air and air bubbles up and out.