The "Gas Phase" refers to one of the states of matter where substances exist as gases. In this phase, particles are widely spaced and move freely, allowing gases to fill their containers completely. The behavior of gases is often described by the Ideal Gas Law, which relates pressure, volume, temperature, and the number of particles. Gases have unique properties, such as low density and high compressibility. Unlike solids and liquids, gases do not have a fixed shape or volume. Common examples of gases include oxygen, carbon dioxide, and nitrogen, which are essential for various biological and chemical processes.