Crush The Can

Physics

Pressure, Vacuums

Grade Range

Elementary School, Middle School, High School

Format

Stage

Materials

   * An empty aluminum soda can
   * Bowl with water
   * Heat resistant gloves
   * Propane torch
   * Can holder (ring shaped holder)
   * Small blast shield 

Safety Precautions

Please read the Fire Demonstration Safety and Loud Demonstration Safety sections of the Demonstration Safety page before performing this demonstration.

This demonstration requires: safety glasses, heat gloves, fire extinguisher, blast shield

Demonstration

Prepare the demonstration: Fill the bowl with water, and set the blast shield in front of the bowl. Put a small amount of water in the can, measuring less than an inch deep inside the can (approximately 10mL). Set the can in the ring holder. Put on the safety glasses and heat gloves.

1. Hold the can holder in one hand, and the blowtorch in the other. Turn on the blowtorch, and heat the bottom of the can, moving the blowtorch flame in a small circle.

2. Once the water starts to boil, have the assembly give a countdown. At the end of the countdown, flip the soda can, open end first, into the bowl of water. It should crush!

3. Turn off the blowtorch, and lift the soda can out of the bowl, allowing the water to drain. Wear the gloves while removing the can from the holder, as it may still be hot.

Why This Works

Pressure is when a force is applied over an area. Air pressure refers to the force that the air around us is constantly applying on us. We don't normally notice the effect of the air pressure around us, but we can by using this can.

When we heated the water in the can, we made it boil and start to evaporate. liquids take the shape of the container they are in, while gases take up all of the space within a container that they can. The steam caused the rest of the air to leave the can, meaning that it only had steam and water inside of it while the water was boiling in the can. When the can was then flipped into the water, the steam inside of it condensed back to a liquid. This left a lot of empty space in the can, which we call a vacuum. The walls of the can could push back while it had gas inside to push against the gas outside. But, when we had no gas left inside the can, the gas outside the can was able to crush it!

Additional Information

• This demonstration benefits from being performed twice in a row. The first time is to show the students and get them thinking, the second time is to explain the different parts of the experiment.
• This demonstration is a part of the Pressure Show.