The amount of gas that dissolves in a liquid is proportional to:

The phenomenon where the amount of gas that dissolves in a liquid is proportional to the partial pressure of that gas is governed by Henry's Law. This law states that, at a constant temperature, the amount of the gas dissolved in a liquid is directly related to the partial pressure of that gas above the liquid. In a diving context, this principle is critical because as divers descend, the pressure increases, resulting in more gas being able to dissolve in the blood and other tissues.

When a diver ascends and the pressure decreases, the amount of dissolved gas also decreases, which can lead to problems such as decompression sickness if the gases come out of solution too quickly. Understanding this relationship is essential for safe diving practices, as it helps divers manage their exposure to various gases at different depths.

Other options do not accurately represent this relationship. While the water temperature can affect gas solubility, it is not the primary factor described by Henry's Law. Similarly, the amount of gas already in the liquid does not influence the rate of additional gas dissolving as directly as partial pressure does. Lastly, gauge pressure, particularly at sea level, does not pertain directly to the amount of gas in the liquid in the way partial pressure does.