PADI Divemaster Certification Practice Exam

What happens to a liquid in contact with a gas when the pressure is increased?

1. The liquid evaporates

2. It becomes saturated immediately

3. Gas dissolves until the liquid saturates

4. The gas escapes from the liquid

The correct answer is: Gas dissolves until the liquid saturates

When the pressure is increased on a liquid in contact with a gas, the gas tends to dissolve more readily in the liquid. This is explained by Henry's law, which states that the amount of gas that can be dissolved in a liquid is proportional to the pressure of the gas above the liquid. As the pressure increases, the solubility of the gas in the liquid increases, allowing more gas molecules to enter the liquid until the point of saturation is reached. This scenario is often encountered in practical diving situations, where increasing pressure can lead to a higher concentration of gases, such as nitrogen and oxygen, being dissolved in the diver's body fluids. It's essential for divers to be aware of this phenomenon, particularly with respect to managing risks associated with gas saturation during decompression.