Wide-mouth glass drink bottle (ex: a Starbucks Frappuccino bottle - the mouth needs to be a little smaller than the egg. The size of the bottle will depend on the size of the eggs )
Vegetable oil
Matches
Strips of paper folded a couple times lengthwise (slightly shorter than the bottle)
Water
Procedure
Hard boil the eggs the night before the experiment.
Use a paper towel to coat the inside edge of the bottle mouth with a little bit of vegetable oil for lubrication.
Peel one of the eggs, then dip it in water and set it with the small end down in the mouth of the glass bottle. It should be slightly larger than the mouth of the bottle, so it doesn't fit inside.
Use a match to light the end of a strip of paper on fire. Lift the egg off the bottle, drop the paper inside with the flame down, and quickly replace the egg. Watch the egg get sucked inside!
Science Behind It
Air pressure! When the burning paper is dropped into the bottle, it causes the air inside to heat up and expand rapidly. That expanding air pushes the egg aside and it escapes from the bottle. When the fire consumed all the oxygen inside the bottle, the flame went out and the remaining air in the bottle cooled down. Cool air takes up less space, exerting less pressure inside the bottle. The result was an unbalanced force of the air pushing on the egg from outside being greater than the force of the air pushing up on it from inside the bottle.
Egg in a Bottle Video
Tips
It is very important to hard boil the eggs the day before the experiment, and project leaders should try the experiment themselves before members arrive, to ensure the mouth of the bottle is good size for the egg.