Paper 2 · November 2019 · Biology
Exhaled air is warmer than inhaled air because
Athe air is warmed to body temperature while it is inside the air passages and lungs.
Bthe lungs squeeze the air during breathing out, and squeezing a gas raises its temperature.
Cair rubs against the walls of the windpipe as it moves, and this friction heats it up.
Dcarbon dioxide is a warm gas, so air rich in carbon dioxide is warmer than ordinary air.
Explanation
Air drawn in at room temperature passes over the moist, well supplied linings of the nose, windpipe and lungs, where warm blood gives up heat to it. It therefore leaves the body at about body temperature, which is usually higher than the temperature of the surrounding air.
Derived from ZIMSEC Combined Science 4003/2, November 2019, Q1(a)