Final answer:
The compression of a sealed plastic bottle when taken from a high to a lower altitude is due to changes in atmospheric pressure, causing a pressure differential between the inside and outside of the container.
Step-by-step explanation:
When you seal a soft plastic bottle or juice container at a high altitude and then return to lower altitude, the container may appear dented inward due to the change in atmospheric pressure. In the mountains, the atmospheric pressure is lower than in the valley, so when you seal the container, the pressure inside it balances with the lower external pressure. Upon descending, the external atmospheric pressure increases, but the air inside the bottle cannot equalize with the new higher pressure as the bottle is sealed. This causes a pressure differential, with higher pressure outside the bottle and lower pressure inside, leading to the compression of the soft container.
Henry's Law relates to the solubility of gases in liquids and describes how gas solubility changes with pressure. When a soft drink or sparkling water is bottled at a high pressure with CO₂, the gas is dissolved in the liquid according to Henry's Law. If this sealed bottle was taken from a high altitude to a lower altitude without opening, similar principles apply; the pressure inside remains constant while the external pressure increases, potentially compressing the container.