Gases lack a fixed form; their volume and configuration are dictated by the container they occupy. Unlike solids, which maintain a rigid structure, or liquids, which possess a definite volume but conform to their surroundings, gases expand to fill all available space. For example, if a small amount of helium is released into a large, empty room, it will disperse evenly throughout the room, assuming its shape and volume.
The absence of a specific form is fundamental to many physical and chemical processes. This property facilitates the diffusion of substances, enabling vital processes such as respiration in living organisms and the efficient mixing of reactants in industrial applications. Historically, understanding this characteristic was crucial in developing pneumatic devices and comprehending atmospheric phenomena.
