This classic physics demonstration is used to show the effects of pressure difference between the atmosphere and a cooling volume of air. With a set of clean apparatus, you can even have the egg for a snack after that.
- Hard-boiled Egg
- Flask or glass bottle with mouth smaller than the egg
- Paper measuring about 2 cm by 5 cm
- Peel the hard-boiled egg.
- Light the piece of paper and drop it into the flask.
- Place the peeled egg on the mouth of the flask such that the egg seals the flask.
- Observe the egg being sucked in while the flame dies.
When the burning paper enters the flask, it causes the air within the flask to heat up and expand, with some escaping from the flask. When the egg seals the flask, the flame dies as the paper is about to be burned up while oxygen is also running out.
The air then cools down and the pressure within the flask drops. The pressure due to the atmosphere acting downward on the egg is then greater than that acting upward due to the pressure of the cooling air. This pushes the egg into the bottle.