Chemistry plays a critical role in daily life, impacting areas such as medicine and health, consumer products, energy production, the ecosystem, and many other areas. Communicating about chemistry in informal environments has the potential to raise public interest and understanding of chemistry around the world. However, the chemistry community lacks a cohesive, evidence-based guide for designing effective communication activities. This report is organized into two sections. Part A: The Evidence Base for Enhanced Communication summarizes evidence from communications, informal learning, and