Chapter 31, Problem 6RQ

To determine

The reason behind the fact that warmer air rises and in expands when it cools.

Answer to Problem 6RQ

The warm air rises and cools as it expands are due to condensation.

Explanation of Solution

As the air cools, the temperature of the air decreases and water vapor in the saturated air condenses. Because of the fact that the slower-moving molecules characterize slow, low temperatures, saturation and condensation are more likely to occur in cool air than in warm air. The expansion occurs when the air cools is that the water molecules move slower and condensation occurs. The molecules of the warm air are fewer in the given volume, and it absorbs the energy in the form of heat to make its density less as compared to cold air. So the warm air rises.

As the warm air rises and expands, the pressure falls as the elevation increases and corresponds to its temperature, decreases. As a result, the air cools as it expands.

Conclusion:

Therefore, the warm air rises and cools as it expands are due to condensation.