Substances lacking a fixed form and occupying space without maintaining a constant quantity are commonly referred to as gases. These materials expand to fill any available enclosure and can be readily compressed. A familiar example is the air we breathe, which consists of a mixture of various elemental and compound gaseous substances.
The characteristic behavior of these substances underpins numerous industrial processes, meteorological phenomena, and biological functions. Understanding their properties is crucial for designing efficient engines, predicting weather patterns, and comprehending respiratory mechanisms in living organisms. Historically, the study of these substances has led to the development of fundamental laws governing the behavior of matter and energy.