Eggs-Periments: Bottled Egg

First get permission to use kitchen equipment and eggs.

One peeled, hard-boiled egg
Plastic or glass bottle with an opening slightly smaller than the egg
Large bowl of hot water
Large bowl of ice water

Put the bottle in the bowl of hot water for about five minutes.
Move the bottle to the bowl of ice water. Wet the egg and place it pointed side down in the bottle opening. As the air inside the bottle cools, the egg will slowly move into the bottle.
To remove the egg, hold the bottle upside down so the egg is near the opening. Blow hard into the bottle with your mouth tight against the opening. Point the bottle away from you: The egg flies out!

Hot air expands. Cold air contracts. When the air inside the bottle is heated, the molecules, or tiny air particles, inside the bottle spread out, increasing air pressure. As the air in the bottle cools, the air pressure decreases. The greater outside air pressure pushes the egg into the bottle. Blowing into the bottle raises the air pressure again. The air and the egg rush out of the bottle.