What happens to air pressure and the amount of oxygen as the altitude increases in Earth's atmosphere?
As the altitude increases in Earth's atmosphere, the air pressure decreases. This means that the molecules of air are more spread out and the density of the air decreases. As a result, the atmospheric pressure decreases with increasing altitude.
The amount of oxygen in Earth's atmosphere also decreases as the altitude increases. However, the decrease in oxygen concentration is relatively constant compared to the decrease in air pressure. This means that even though the percentage of oxygen in the air remains constant at around 21%, the actual amount of oxygen molecules present in a given volume of air decreases with increasing altitude due to the decrease in air pressure.