Important Characteristics of Gases
Gases are highly compressible An external force compresses the gas sample and decreases its volume, removing the external force allows the gas volume to increase.
Gases are thermally expandable When a gas sample is heated, its volume increases, and when it is cooled its volume decreases.
Gases have low viscosity Gases flow much easier than liquids or solids.
Most Gases have low densities Gas densities are on the order of grams per liter whereas liquids and solids are grams per cubic cm, 1000 times greater.
Gases are infinitely miscible Gases mix in any proportion such as in air, a mixture of many gases.