Physics and Gas Laws Flashcards

A diver fills a lift bag with 30 liters of air at 30 meters (4 ATA). When the bag reaches the surface, its volume will be approximately:

Answer: 120 liters

Boyle's Law: V2 = (P1 × V1) / P2 = (4 × 30) / 1 = 120 liters at the surface.

Which property of water makes it denser than air and affects a diver's buoyancy?

Answer: Water molecules are more closely packed together

Water's density (1000 kg/m³ vs ~1.2 kg/m³ for air) comes from the close packing of its molecules.

The partial pressure of nitrogen at 40 meters (5 ATA) breathing air (79% N2) is:

Answer: 3.95 ATA

ppN2 = fraction × total pressure = 0.79 × 5 = 3.95 ATA.

Why do colors disappear at depth in the order red, orange, yellow, green, blue?

Answer: Water absorbs longer wavelengths (red end) of light first

Water absorbs red light most strongly, then progressively shorter wavelengths, causing colors to disappear in order of wavelength.

An oxygen-enriched air (EANx) mix with 32% O2 reaches its maximum operating depth when ppO2 reaches 1.4 ATA. What is that depth?

Answer: 111 feet (34 m)

Max ATA = 1.4 / 0.32 = 4.375 ATA → depth = (4.375 - 1) × 33 ≈ 111 feet (33.75 m, rounded to 34 m).

The ideal gas law (PV = nRT) tells us that when a cylinder is filled rapidly, the air heats up. This is an application of:

Answer: Gay-Lussac's Law and Charles's Law combined

Rapid compression raises temperature (Gay-Lussac's/Charles's relationship); as gas cools, pressure drops slightly — the hot fill effect.

A diver is neutrally buoyant with a full tank. As they consume air during the dive, they will tend to become:

Answer: More positively buoyant

As air is consumed, the tank and diver system loses mass (the expelled gas) while displacing the same water volume, increasing net buoyancy.