Which of the following demonstrates an altitude effect described by Boyle's Law?

• A. A passenger experiences tooth pain upon ascent
• B. A 50 degree drop in outside temperature when you ascend to 30,000 ft.
• C. Nitrogen bubbles dissolve into tissues upon ascent to 25,000 feet in an unpressurized cabin
• D. A passenger experiences severe cramping and bloating upon descent to the airport

Answer: (A)

Gas expands when ambient pressure drops, a direct result of Boyle’s Law (P1V1 = P2V2 at constant temperature). As you ascend, external pressure falls, so any gas trapped in a closed space can increase in volume and push on surrounding structures. The tooth pain reported on ascent fits this idea: tiny gas pockets within dental structures or fillings can expand as cabin pressure decreases, irritating nerves and causing pain. The other options don’t illustrate gas-volume change with altitude: a temperature drop is environmental, not a gas-volume effect; nitrogen bubbles forming or dissolving on ascent/descent describes decompression phenomena in tissues rather than a straightforward volume expansion in a closed space; and cramping or bloating on descent involves different pressure-gas dynamics not aligned with this altitude-related expansion.