“A box without hinges, key or lid, yet golden treasure inside is hid.” This is perhaps my favorite riddle from “The Hobbit” by J.R.R. Tolkien. The answer is, of course, an egg; the largest cell in the world. (The ostrich holds that record).

So what can we do with an egg that is science-like and fun? Why, dissolve the shell with a mild acid and turn the innards to a rubbery substance, of course.

Without further ado, let’s go.

Materials:

An egg (either cooked or raw… however brave you’re feeling), a tall drinking glass, white vinegar.

Procedure:

• Put your egg into a tall drinking glass.
• Pour vinegar into the glass until the egg is covered.
• Put the glass aside so no one drinks and/or spills it. It will smell a bit. Vinegar has a strong odor.
• Let the egg soak overnight. Make some observations! You should notice a lot of foam and bubbles. When it seems to have slowed, move on to the next step.
• Rinse the vinegar and foam out with water and then cover the egg again with vinegar.
• Wait for 6 days. That’s a long time but do it; you don’t want a half pickled egg in your hands.
• At the end of this time, rinse off the egg and pick it up.
• You should notice it feels slightly different than when you started… most noticeably it is missing the shell and has a weird rubbery feel to it. Shake it. Gently squeeze it.
• Test out your new creation in the sink by dropping it from a few inches and then some more.
• You now have a cool creation that can astound your friends and family. Place it back in the egg tray for some hilarity. The possibilities are endless.

Explanation:

A chicken’s egg is covered in a shell that is made of calcium carbonate. That’s a complex arrangement of carbons, calcium, and oxygen. Regular vinegar is made of acetic acid. You all know when you mix vinegar and baking soda what a strong reaction you get. The shell is made of the same “carbonate” and will react like soda, only much less extreme. The little bubbles you see in the water are made of carbon dioxide gas; just like the bubbles from your vinegar and baking soda volcano.

Once the shell is gone, the vinegar will cross over the semi-permeable membrane (through a process called “osmosis”) and slightly inflate the egg. This process also “pickles” the egg, by hardening it up. The toughening of that membrane is what lets you bounce it on the counter, roll it along the floor, and whatever trickery (I mean science) you want to do with it!

Experiment Further:

As with all science, the real experimenting takes place after you see the trick. Now that you know how to do this to an egg, what can you change about the system to experiment?

Do all eggs take the same time? Do they all get as bouncy? What about brown eggs versus white ones? Free-range organic versus cage raised shells… are they different? Does the type of vinegar matter? Keep experimenting!

I hope you enjoyed this simple experiment.  If you have more questions about this, or need tips about science fair ideas around this topic (or others), contact the author.

Steve Davala is a middle school science teacher who likes to write and work with Photoshop. He’s got two kids of his own and subjects them to these science activities as guinea pigs.