-A-
Acid	a substance with a high concentration of hydrogen ions (less than 7 on the pH scale); a substance that can donate a proton; normally characterized with a sour taste, the ability to react with certain bases and metals to form salts, and turning litmus paper red
Alkaline	see base
Atom	smallest unit of an element

-B-
Base	a substance with a low concentration of hydrogen ions (greater than 7 on the pH scale); a substance that can accept a proton; normally characterized with a bitter taste, the ability to react with acids to form salts, and turning litmus paper blue
Buffer	a substance that minimizes change in the acidity of a solution when an acid or base is added to the solution

-E-
Electron	stable matter below the size of an atom having a negative charge

-I-
Ion	an atom or a group of atoms that has acquired a net electric charge by gaining or losing one or more electrons

-L-
Litmus	water-soluble blue powder derived from certain lichens that changes to red with increasing acidity and to blue with increasing basicity
Litmus Paper	paper coated with litmus that is used as an acid-base indicator

-M-
Molecule	the smallest particle of a substance that retains the properties of the substance and is composed of two or more atoms

-P-
pH Scale	p(potentional of) H(hydrogen); a logarithmic scale used as a measure of the acidity or alkalinity of a solution
Proton	stable matter below the size of an atom having a positive charge

-R-
Reactive	tending to participate readily in reactions; substances located on the extreme ends of the pH scale