Explore fundamental concepts in chemistry through this 14-minute video lecture from Khan Academy. Learn about atomic mass units (AMU) and their significance in measuring atomic-scale masses. Discover Avogadro's number and its crucial role in defining the mole, bridging the gap between atomic-level particles and measurable quantities. Understand molar mass and its expression in grams per mole, enabling conversions between substance mass and molar quantities. Practice calculations involving the number of atoms in a sample and determine the molar mass of compounds like CO2. Gain essential knowledge for stoichiometry and quantitative chemistry analysis through clear explanations and step-by-step examples.