Acid: A substance that tastes sour, react with metals and carbonates, and turns blue litmus red.

Base: A substance that tastes bitter, feels slippery, and turns red litmus blue.

Concentration: The amount of one meterial in a certain volume of another material.

Hydrogen ion: A positivly charged ion formed of a hydrogen atom that has lost its electron.

Hydroxide ion: A negitively charged ion made of oxygen and hydrogen.

Indicator: A compound that changes color in the presence of an acid or base.

PH scale: A mesure of the concentration of hydrogen ions in a solution.