What happens when air rises?

What happens when air rises?

• A. It contracts due to increasing pressure.
• B. It expands because the air pressure increases with height.
• C. It expands due to the decrease in air pressure.
• D. It remains at constant volume as it rises.

Answer: (C)

When air rises, it moves into regions where the atmospheric pressure is lower. To balance the lower external pressure, the rising air parcel expands. That expansion means its volume increases, and as it expands without gaining heat (an adiabatic process), its temperature typically drops. So the air rises and expands because the surrounding air pressure decreases with height. The other ideas don’t fit because pressure does not increase with height, so the air wouldn’t contract; the volume isn’t kept constant as altitude changes, and a rising parcel doesn’t stay the same size.

When air rises, it moves into regions where the atmospheric pressure is lower. To balance the lower external pressure, the rising air parcel expands. That expansion means its volume increases, and as it expands without gaining heat (an adiabatic process), its temperature typically drops. So the air rises and expands because the surrounding air pressure decreases with height. The other ideas don’t fit because pressure does not increase with height, so the air wouldn’t contract; the volume isn’t kept constant as altitude changes, and a rising parcel doesn’t stay the same size.