Bottle Blaster
| Physics: | Air Pressure, Vacuums |
| Grade Range: | High School |
| Format: | Stage |
This demonstration is an exciting way to show students how strong air pressure can be. Be sure to have a trash can nearby to collect the pieces of the bottle after presenting. This demonstration requires a lot of practice before performing.
Materials
- Empty Glass Bottle
- Water
- A Large Towel or Similar
Safety Precautions
Please read the Physical Demonstration section of the Demonstration Safety page before performing this demonstration.
This demonstration requires: Safety Goggles
Demonstration
- Fill the bottle most of the way with water, leaving a small amount of air space at the top. Let the audience know that you are going to be breaking off the bottom of the bottle without touching the bottom. Feel free to ham it up (claim that you are using the force, magic, etc.).
- Place out the towel or similar underneath you and the bottle. Hold the bottle either in front of you, or close to your side, with your non-dominant hand gripping it around the neck. Be sure the bottle is held low, around waist height.
- Strike the mouth of the bottle with your dominant hand, striking it downward with the palm of your hand. Be sure to cover the entire mouth of the bottle when you do so. It may take a few attempts, But when you hit it the bottom of the bottle will fly off, spilling water everywhere!
- Ask the audience for ideas on why this happened. Do you really have special powers? What is the secret to this demonstration?
Why This Works
Pressure is when a force is applied over an area. Air pressure refers to the force that the air exerts on everything around it. We can increase the pressure on something by either increasing the force applied or decreasing the area it is applied to. With this demonstration, we are increasing the pressure applied to the air and water inside the bottle. When the presenter smacks the bottle, they are forcing a small amount of air into the bottle, which increases the pressure inside the bottle. The air, when it experiences the increase in pressure, tries to balance it out by compressing, or taking up less space in the bottle. The water, however, does not compress, so the extra space that the air leaves is taken up by the water. This creates a small vacuum in the bottom of the bottle. The vacuum collapses when the air expands back and pushes the water down. This "water hammer" smacks down hard onto the glass, breaking it off!
Additional Information
- The size and shape of the bottle will affect the quality of the demonstration. A bottle with a small mouth and a wide base works better than one with similar size in mouth and base. Also, the amount of water in the bottle will affect how easily you can break it. The more full the better, but if the bottle is too full then it won't work.
- This demonstration pairs well with the Marshmallow Smashies and the Crush The Can demonstrations.
- This demonstration can be a part of the Pressure Show