From this book:
In the Chemistry section, I did Experiment 196 – Rubbery Egg.
I put an egg in vinegar in a glass, and I waited several days.
Today we went to see the egg. We took it out and it felt rubbery.
Here’s the explanation:
The vinegar reacts with the calcium in the eggshell, dissolving it. This makes the shell rubbery. This shows the importance of calcium to make the shell strong, just like the calcium in are bones.Keep drinking that milk!
I don’t know how but the vinegar must have done something to the calcium in the shell!
When you start to learn about chemistry you will learn why certain compounds like calcium and vinegar react with one another, do to their molecular/atomic structures. It has to do with the number of electrons and protons in the respective compounds and how these atoms are chained together (I think).
Also, you may be interested in Mr. Wizard: http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=mr+wizard&x=0&y=0
He used to have a TV show where he did experiments like the ones you’re working on, for young scientists. He also has a few books with other experiments you can try.
Though, I am sure you can find free experiments all over the web if you search for them!