The Swollen Egg|
Soak the egg in vinegar until the shell has become soft. Pour out the vinegar and soak the egg in plain water. In a few days the egg will have become so large that the shell will burst.
Without the vinegar treatment, peel just a little square of eggshell off the egg, without breaking the membrane below. By osmosis, the water will go into the egg, pressing upward on the exposed membrane until it breaks.
The acid in the vinegar combines with the calcium in the eggshell, making the shell soft. When the egg is then immersed in water, the water will go through the shell into the egg until the shell bursts. This is the principle of osmosis, in which a less concentrated solution will go through a membrane into a more concentrated solution