This demonstration will show that carbon dioxide is more dense than
air, and will be drawn to the bottom of a container by the force of
Time requirement: 15 minutes as a demonstration. The demonstration
will take more time if a fire extinguisher is not available.
- Fish tank and lid
- CO2 fire extinguisher if available
- Baking soda (if extinguisher is not available)
- Vinegar (if extinguisher is not available)
- Soap bubble solution
- Bubble blowing device
- Discharge a one-second blast of carbon dioxide from the fire
extinguisher (if available) into the fish tank. Place the lid on the tank.
If an extinguisher is not available, add a mixture of one part baking
soda to three parts vinegar to the bottom of the tank. The amounts
necessary to generate enough gas for your tank depends on the size of the
- Remove the lid and blow bubbles into the tank. Be careful not to
disturb the CO2 gas in the tank.
- Observe what happens to the bubbles in the tank.
- Describe what happened when the bubbles were added to the tank.
- Why did the bubbles not fall to the bottom of the tank?
- What makes the carbon dioxide sink to the bottom of the tank?
- What would happen if another gas were added to the tank which was more
dense than air but less dense than carbon dioxide?
- How did the size of the bubbles affect the way they reacted when
they were introduced to the tank?
- If no more carbon dioxide were added to the tank, would the bubbles
continue to float on the carbon dioxide? Why???
Last updated: August 27, 1997
Joe Twicken /