Home Science Experiment: The Egg and the Bottle
This experiment is probably a classic home experiment that anyone can try. It doesn’t require much at all but it’s really fascinating. The task is to cause a boiled egg to go through a narrower bottle opening without busting. Gravity alone won’t make this Humpty Dumpty fall! You’ll be manipulating air pressure within the bottle to make this work.
What do you need?
- A boiled egg -- preferably hard. The soft boiled eggs may get messy.
- A glass bottle -- with an opening of diameter that is a bit smaller than that of the diameter of the egg.
- Lighter + Paper (depends on method used)
- Icy Cold Water (depends on method used)
- Warm Water (depends on method used)
How to do it?
The Heating Methods
Using a lighted paper
- After you have your egg boiled and ready, you can strip the shell away.
- Light the paper and drop it inside of the bottle.
- Place the smaller end of the egg into the mouth of the bottle.
- Watch to see the egg descend into the bottle as the bottle cools.
Using hot water
Instead of using the lighted paper, you could also use very hot water. Run hot water from a tap on the bottle, then place the egg (smaller end pointing down) in the opening of the bottle. Set the bottle with egg on a table and as the bottle cools the egg will descend through the bottle opening.
The Cooling Method
Instead of using warm water as described above, you would use cold water instead. Immerse the glass bottle into very cold water for a bit. Place the egg (smaller end pointing down) into the mouth of the bottle. Watch and witness the egg descending.
How does all this work?
The core of this experiment is based on manipulating air pressure in the glass bottle. Naturally, the pressure inside and outside of the bottle is the same. When you heat the bottle, you’re effectively heating the air inside the bottle. It is known in Thermal Studies that when you have a gas in a constant volume and you heat it, you’ll increase the pressure of that gas. This means that temperature of a gas is proportional to its pressure once its volume is kept constant. This is in fact Gay-Lussac’s Law.
By using the heating methods, you may find that the egg is being pushed upwards by the increased air pressure inside the glass bottle. Heated air rises and will escape thereby decreasing the pressure inside of the bottle. What will happen is that the pressure outside the bottle will eventually be more than the pressure inside the bottle, which causes a net force on the egg. The egg will be pushed inside of the bottle, and of course gravity plays its role.
When the bottle is cooled, the temperature of the air inside the bottle is lowered. This means that there will be a drop in pressure according to Gay-Lussac. Here again, the pressure outside of the bottle will be greater than the pressure inside of the bottle. The egg will once again be pushed by the greater air pressure outside of the bottle.
So, what if you want to get the egg out the bottle?
The answer to this goes right back to the principle. If you can increase the pressure of air inside of the bottle, the egg will be pushed out. How to do this? Try blowing inside the bottle and allowing the egg to quickly fall into the opening (smaller part pointing out). It may require a little skill, but of course this is not the only way to do it. Think about it :)