The core of understanding phases of matter is to understand the Particle Theory. This theory and its many versatile applications are explained in this book. The subject is broken down into bite-sized activities that can be performed in a classroom setting as well as by students at home. Some are wuick experiments; others include observations over many weeks. All are unified by explaining how matter interacts with other matter, how phases are changed by external influences, also how all that matter matters to us. 96 pages.