According to Boyle's law, if the ambient pressure doubles, the volume of a trapped gas

• A. Increases
• B. Remains the same
• C. Decreases by one-half
• D. Increases by a factor of four

Answer: (C)

Pressure and volume are inversely related for a gas when temperature stays constant. Boyle's law tells us that the product of pressure and volume remains the same as pressure changes. So if the ambient pressure doubles, the volume must shrink to keep P×V constant. Mathematically, V2 = V1 × (P1/P2); with P2 = 2P1, V2 = V1 × (1/2). That means the volume decreases by half. This reflects how squeezing a gas (increasing pressure) reduces its available space, while cooling or heating would complicate things beyond this simple inverse relationship.