Materials Required
  • Peeled hard-boiled egg
  • A jar with opening slightly smaller than the diameter of the egg
  • Paper/lighter

How to do it

  • Set a piece of paper on fire and put it into the bottle.
  • Set the egg on top of the bottle (small side pointed downward).
  • When the flame goes out, the egg will get pushed into the bottle.

Explanation

If you just set the egg on the bottle, its diameter is too large for it to slip inside. The pressure of the air inside and outside of the bottle is the same, so the only force that would cause the egg to enter the bottle is gravity. Gravity is not sufficient to pull the egg inside the bottle.

When the temperature of the air inside the bottle is changed by putting the fire inside, there is a change in the pressure of the air inside the bottle. Hence the as the pressured decreases inside the bottle to equalize the pressure, it tends to pull the object inside. Hence the egg is pulled inside the jar.