Wikijunior:Big Book of Fun Science Experiments/Osmosis in eggs
- an egg
- A beaker
- Some water
- a pin
What to do 
Step one. Put the egg carefully into a beaker of vinegar.
Step two. Leave the egg overnight.
Step three.Take the egg out of the vinegar and the shell would have gone.
Step four.Put your egg that doesn't have any shell on it into a bowl of clean water and leave over night.
Step five.The egg will swell up and then poke it with a pin and it will squirt out like a fountain.
Vinegar, due to its acidity, will break down the calcium carbonate shell of the egg. This can be clearly visible in a change of the vinegar color. When you put the egg into water, a process called osmosis happens. The egg tries to maintain a balance of water inside the egg to that outside of the egg, so it will take in large amounts of the water it is currently in, making it swell.