Acids and bases are terms used to refer to how different elements, compounds, or solutions interact with each other. Water can be used to distinguish an acid from a base. A water molecule consists of one hydrogen atom and two oxygen atoms. Imagine adding a chemically reactive substance to water. Upon contact, the molecules of the substance break the bonds of water molecules, causing the water molecules to lose a hydrogen ion. When this occurs, the substance is considered an acid. Now imagine adding a different substance to the water. In this case, the water molecules lose a hydrogen atom and an oxygen atom. The liberated oxygen and hydrogen atom bond to form a hydroxide ion. In this case the substance added to the water is considered a base because it created hydroxide.

The release of hydrogen ions or hydroxide ions can be detected by checking the pH level of the water. pH is measured on a scale of 1-14. If the pH is between 1-6 then the solution is considered an acid. If the pH is between 8-14 it is considered a base. A pH of 7 indicates a neutral solution.

Both the seashell and the egg shell are made of calcium carbonate. The Mollusk is a class of invertebrates such as snails, squid, octopus, and clams. Many sea mollusks secrete nacre, a substance that mollusks use to create their shell. In oysters, nacre is the substance that creates pearls. Nacre is made of calcium carbonate, as is the shell of the egg. Calcium carbonate is considered a base. On the other hand, vinegar is acidic.

When and acid and base come into contact, a chemical reaction occurs. In the case of the sea shell and the egg, the acidic vinegar breaks down the calcium carbonate, dissolving the sea shell and egg shell.