Gas Properties Definitions Aerodynamics involves the interactions between an object and the surrounding air. To better understand these interactions, we need to know some things about air. Individual atoms can combine with other atoms to form molecules. Under normal conditions, matter exists as either a solid, a liquid, or a gas.
Air is a gas .
In any gas, we have a very large number of molecules that are only weakly attracted to each other and are free to move about in space. When studying gases, we can investigate the motions and interactions of individual molecules, or we can investigate the large scale action of the gas as a whole. Scientists refer to the large scale motion of the gas as the macro scale and the individual molecular motions as the micro scale . Some phenomenon are easier to understand and explain based on the macro scale, while other phenomenon are more easily explained on the micro scale. Macro scale investigations are based on things that we can easily observe and measure .