Placing a raw whole egg in vinegar is a good experiment that teaches a fundamental principle of chemistry—the interaction between an acid and a base. Submerging a raw whole egg in a jar of white vinegar and refrigerating it for 72 hours produces a “rubber egg” because the vinegar dissolves the egg shell surrounding the egg’s inner membrane.
Egg shells are composed of calcium carbonate, which is an organic compound also found in limestone, chalk, marble and coral. Vinegar contains acetic acid, the substance giving vinegar its sour taste.
The vinegar’s acetic acid breaks down the calcium carbonate crystals in the egg shell into separate calcium and carbonate parts with the by-product of water. The calcium part takes the form of calcium ions, which is suspended in the vinegar and water. The carbonate part takes the form of carbon dioxide gas which bubbles off as the egg shell dissolves.