This is a series of videos directed to high school honors or Pre-AP Chemistry. The concepts of the mole and Avogadro’s number are introduced. Students learn how to determine the molar mass using the periodic table and from experimental data. Dimensional analysis is used to convert among mass, mass within a substance, moles, representative particles (atoms, formula units, molecules) and atoms within a substance. The Law of Constant Composition is introduced and the percent composition by mass of a substance is calculated. Empirical formulas and molecular formulas are calculated from composition (not combustion). Hydrate formulas are determined from percent or mass composition.