Boyle's Law: Inverse Relationship Between Pressure and Volume at Constant Temperature

Steps:

• Ideal gas law PV = nRT applies; temperature T and moles n are constant.
• Volume V decreases, so pressure P must increase to maintain equality.
• At molecular level, constant T means average kinetic energy and speed unchanged.
• Smaller V crowds molecules, increasing collision frequency with piston and walls.

Why C is correct:

• Boyle's law states P ∝ 1/V at constant T; reduced volume raises pressure as molecules collide more frequently with the piston per unit time.

Why the others are wrong:

• A: Pressure increases, not decreases; less room causes more frequent collisions, raising force on walls.
• B: Constant T means molecules maintain same speed, not slower movement.
• D: Constant T allows pressure to change with volume via Boyle's law.

Final answer: C