Geology Air density Pressure

  Geology Air density Pressure   Lab 8–Air Density, Pressure, and Temperature Please make your answers highlightedin yellow. Air Density and Air Pressure The atmosphere is made up of a mixture of several gases - though it is mostly nitrogen and oxygen - and is held to the Earth by the force of gravity. Because a gas is compressible, gravity pulls most of the gas molecules close to the surface of the Earth. This implies that the weight of the air overhead is greatest at the Earth's surface, and this weight decreases with height. Another way of stating this fact is to say that the density of the atmosphere decreases with height where density in this context is defined as the mass (measured in grams or kilograms) of the air contained in a unit volume (measured in cubic centimeters or cubic meters). At sea level air has an average density of about 1.2 kg per cubic meter.