The first chapter of the Kerala State Class 9 Physics book introduces the subject of physics and its importance in our daily lives. It explains the basic concepts of physics such as matter, energy, and their interrelation. The chapter also discusses the different branches of physics and their applications in various fields. It emphasizes the need for scientific inquiry and experimentation to understand the laws of nature. Overall, the chapter provides a brief overview of the subject of physics and its relevance to our world.