CHEM 31A is the first course in a two-quarter sequence designed to provide a robust foundation in key chemical principles for students with a basic background in high school chemistry, who have already placed into Math 19 or higher. The course engages students in group problem-solving activities throughout the class periods to deepen their ability to analyze and solve chemical problems. Students will also participate in a weekly laboratory activity that will immediately apply and expand upon classroom content. Labs and write-ups provide practice developing conceptual models that can explain qualitatively and quantitatively a wide range of chemical phenomena. The course will introduce a common language of dimensional analysis, stoichiometry, and molecular naming that enables students to write chemical reactions, quantify reaction yield, and calculate empirical and molecular formulas. Stoichiometry will be immediately reinforced through a specific study of gases and their properties. Students will also build a fundamental understanding of atomic and molecular structure by identifying interactions among nuclei, electrons, atoms and molecules. Through both lab and in-class exploration, students will learn to explain how these interactions determine the structures and properties of pure substances and mixtures using various bonding models including Lewis Dot, VSEPR, and Molecular Orbital Theory. Students will identify and quantitate the types and amounts of energy changes that accompany these interactions, phase changes, and chemical reactions, as they prepare to explore chemical dynamics in greater depth in CHEM 31B. Special emphasis will be placed on applying content and skills to real world applications such as estimating the carbon efficiency of fossil fuels, understanding hydrogen bonding and other interactions critical to DNA, and calculating the pressure exerted on a deep-sea diver.