Crush the Pop Can

2B30.15

Brief Description

In this classic demonstration of atmospheric pressure and the rapid phase change of water a small amount of water is boiled inside an aluminum soda can until the resulting steam displaces the air, filling the volume with high-energy water vapor. When the can is quickly inverted into a cold water bath, the seal created by the water surface causes the steam to condense almost instantly back into a liquid. This creates a partial vacuum inside the can, leading to a massive pressure differential. Because the external atmospheric pressure (Patm ≈101 kPa) is no longer balanced by internal gas pressure, the surrounding air exerts an inward force that causes the can to implode violently and instantaneously.

Materials Needed

Mini Propane tank, Bunsen burner, and beaker stand, water, aluminum can, container for some water, water, lighter, fire safety equipment (gloves, googles, and fire extinguisher).

Materials for Crush the Pop Can

Setting Up & Performing the Demo

Boil a small amount of water inside a clean soda can using a Bunsen burner. Make sure the tab of the can is only open slightly. Allow time (~30 seconds of boiling) for the water vapor to displace all of the air inside the can. Using heat resistant gloves, quickly overturn the can into a water bath. The can will cool down rapidly, causing the water vapor to condense suddenly. The resulting vacuum inside the can will allow the external atmospheric pressure to crush the can.

A pop can on a bunsen burner A crushed can upside down in a shallow tub of water A man wearing thick gloves holding a pop can upside down in a shallow tub of water

Safety and Other Notes

Proper fire safety needs to be practiced with this demo.

Alternate Set-ups

This demo can be done with a big 55 galloon drum and the water trough from the outreach room.