This lecture introduces the concepts of oxidation and reduction in redox reactions, focusing on the influence of the environment on materials. Topics include the role of acids, bases, and redox reactions, with examples such as metal extraction, batteries, and corrosion. The lecture covers the principles of balancing redox equations, identifying oxidizing and reducing agents, and determining oxidation numbers. Students will learn how to express redox reactions as half-reactions and understand the rules for assigning oxidation states.