• Combustion
• Pressure
• Ideal gas laws

• Hard-boiled egg
• Bottle or flask with an opening slightly smaller than the egg’s diameter
• Paper (a sheet of computer paper or newspaper will do)
• Matches

Note: this experiment involves fire and flammable materials, so adult supervision is a must!

1. Peel the hard-boiled egg.
2. Tear off a piece of paper that can easily fit into the bottle, and carefully light it on fire and drop it into the bottle.
3. Quickly place the egg on top of the bottle, covering the opening.
4. The flame will burn, heating the air inside the bottle. This causes the air to expand, and some of it will push past the egg to escape from the bottle. Recall from our discussion of the ideal gas law that, for a fixed number of particles and volume, the pressure inside the bottle should increase linearly with increases in temperature. The increased pressure is what pushes the air out, and you may even see the egg shake a little as the air escapes. Then the egg will come to rest, covering the opening.
5. Eventually, the fire will burn up all of the paper, or all of the oxygen inside the bottle (whichever comes first), and then the air in the bottle will begin to cool. As it cools, the volume it occupies will decrease, lowering the pressure inside the bottle relative to that outside the bottle. The higher pressure outside the bottle is what pushes the egg through the opening and into the bottle.
6. You can get the egg back out by tilting the bottle upside down and blowing air into the bottle, and then allowing the egg to cover the opening before removing your mouth. Thus you can use the same principle regarding equilibration between high and low pressures to force the egg out.