Gas phenomena refer to the behaviors and properties of gases under various conditions. These include changes in pressure, temperature, and volume, which are described by the Ideal Gas Law. Gases expand to fill their containers, have low density, and can be compressed easily compared to liquids and solids. Common examples of gas phenomena include diffusion, where gas molecules spread out to occupy available space, and effusion, the process of gas escaping through a tiny opening. Understanding these phenomena is essential in fields like chemistry, physics, and engineering, as they play a crucial role in processes such as combustion and respiration.