Final answer:
The density of air decreases as altitude increases, due to the lower atmospheric pressure at higher altitudes. This phenomenon is represented by a downward sloping line on a graph plotting air density against altitude.
Step-by-step explanation:
As altitude is increased, the density of air decreases. This change occurs because the pressure of the atmosphere drops with altitude, leading to less air above a given area, thus decreasing its density. The relationship between altitude and air density can be visualized on a graph, where air density is plotted against altitude, and typically shows a downward sloping line, indicating that higher altitudes have lower air density.
For example, at the altitude of Mount Everest, which is approximately 8,828 meters above sea level, the air density is as low as 0.023 kilograms per cubic meter. Since the temperature can also vary with altitude, it's worth noting that for a constant temperature column of air, the decrease in density approximately follows an exponential trend with altitude. However, temperature variations can affect the rate of density decrease.