How does density of air change with a decrease in temperature?

As temperature decreases, the density of air increases. This phenomenon is explained by the ideal gas law, which states that the density of a gas is directly proportional to its pressure and inversely proportional to its temperature. When the temperature drops, the kinetic energy of air molecules decreases, causing them to occupy less space without changing the overall mass of the air. Thus, a decrease in temperature results in a higher density because the same amount of air mass is contained in a smaller volume.

In a practical aviation context, understanding this relationship is crucial as it affects lift and performance of aircraft. Cold air is denser, which can improve lift at takeoff, while warmer air is less dense, potentially requiring longer takeoff distances.