The Eighth Edition of CHEMISTRY incorporates a strong molecular reasoning focus, amplified problem-solving exercises, and innovative technological resources. This kind of reasoning helps students think at the molecular level and make connections between molecular structure and macroscopic properties. Molecular reasoning and visualization are emphasized via Molecular-Reasoning icons, chapter objectives, end-of-chapter problems, and new artwork, and are integrated into the accompanying technology, including OWL (online homework management system) and General ChemistryNow? (student assessment program). As in previous editions, thermochemistry is covered mainly in one chapter (Chapter 15) and begins the second half of the course. However, to address the need for more material on thermochemistry earlier in the course, the text now includes information on bond energies in Chapter 7 on Chemical Bonding. The discussion of entropy in Chapter 15 has been expanded to include not only molecular disorder but also the concept of energy dispersal.