A GAS<\/a> is one of the four fundamental STATES-OF-MATTER<\/a>, defined by its lack of a fixed shape or volume. In the gaseous phase, atoms or molecules move freely and at high speeds, filling the entirety of any available space. This state of matter is highly compressible compared to solids and liquids. The KINETIC-MOLECULAR-THEORY<\/a> provides the framework for understanding how gas particles interact, emphasizing that their collisions with container walls generate PRESSURE<\/a>.<\/p> Mathematical relationships known as gas laws describe the behavior of GAS<\/a> under varying conditions. BOYLES-LAW<\/a> describes the inverse relationship between pressure and volume, while CHARLES-LAW<\/a> relates volume to temperature. These are synthesized with AVOGADROS-LAW<\/a> into the IDEAL-GAS-LAW<\/a>. These principles are essential in fields such as AERODYNAMICS<\/a> and CHEMICAL-ENGINEERING<\/a>.<\/p> Common substances found in the gaseous state include NITROGEN<\/a>, OXYGEN<\/a>, and CARBON-DIOXIDE<\/a>. The NOBLE-GASES<\/a>, such as HELIUM<\/a> and ARGON<\/a>, are distinctive for their low chemical reactivity. Scientific resources regarding the properties of gases can be found at Britannica<\/a> and NASA<\/a>.<\/p>