PADI Divemaster Certification Practice Exam

What can occur when pressure is reduced in a gas that is in contact with a liquid?

1. Gas dissolves more

2. Liquid boils

3. Bubbles may form

4. Temperature decreases

The correct answer is: Bubbles may form

When the pressure is reduced in a gas that is in contact with a liquid, bubbles may form due to the decrease in gas solubility. This phenomenon is linked to Henry's Law, which states that the amount of gas that can dissolve in a liquid is directly proportional to the pressure of the gas above the liquid. When the pressure decreases, the gas that is dissolved in the liquid comes out of solution, leading to the formation of bubbles. As the pressure drop occurs, the gas molecules that were previously dissolved in the liquid begin to escape, creating visible bubbles. This process is commonly observed in various scenarios, such as when a diver ascends too quickly or when opening a carbonated beverage. Beyond the obvious formation of bubbles, this is an important concept for divers to understand, particularly regarding the management of dissolved gases to prevent conditions like decompression sickness.