Final answer:
Jenn's belief that air pressure decreases with increasing altitude is correct. This decrease is due to the lower density of air at high elevations, resulting in fewer oxygen molecules and the need for supplemental oxygen for climbers.
Step-by-step explanation:
Among Jenn, Lauren, and Chris, Jenn is correct in her assumption regarding air pressure at the summit of Mt. Kilimanjaro. As altitude increases, the density of the air decreases, which in turn reduces the air pressure. According to Figure A4, a cubic meter of air at sea level is much denser and heavier compared to at high altitudes, like the summit of a mountain.
For example, at 500 meters above sea level, a cubic meter of air weighs about 1 kilogram, while at the top of Mt. Everest, it weighs only 0.023 kilograms. This lower air density means less oxygen available to breathe, which is why climbers often require oxygen tanks to summit high peaks.
Moreover, the atmospheric pressure at sea level is typically around 760 mm Hg (millimeters of mercury) or 100 kPa, and it drastically decreases with increasing altitude. At the summit of Mt. Everest, the atmospheric pressure is only 253 mm Hg. While the altitude of Mt. Kilimanjaro is less than that of Everest, a similar trend of decreasing air pressure with increasing altitude applies.