What effect does decreasing the density of air have on air pressure?

Decreasing the density of air directly results in lower air pressure. Air pressure is defined as the weight of the air above a certain level pressing down on a surface. When the density of air decreases, it means that there are fewer air molecules per unit volume. With fewer molecules available to exert pressure, the overall pressure exerted by the air in the atmosphere decreases.

This effect can be observed in various atmospheric conditions. For example, at higher altitudes, the air density is lower due to the reduced amount of air above. As a result, air pressure decreases with altitude. This principle is fundamental to understanding weather patterns, such as why low-pressure systems are typically associated with stormy weather, as the decreased pressure can lead to rising air, cloud formation, and precipitation.

The other options do not accurately represent the relationship between air density and air pressure.