This document provides an overview of three sections (13.1, 13.2, 13.3) from a chemistry textbook chapter on gases. Section 13.1 describes gas laws including Boyle's law, Charles' law, Gay-Lussac's law, and the combined gas law. Section 13.2 introduces the ideal gas law, Avogadro's principle, and compares real and ideal gases. Section 13.3 explains how to use gas laws and stoichiometry to solve problems involving gaseous reactants and products in chemical equations.