Temperature Decrease in Constant Volume Gas

Steps:

• Kinetic energy of gas molecules is directly proportional to absolute temperature (KE ∝ T).
• Decreasing temperature reduces average kinetic energy of molecules.
• Ideal gas law PV = nRT applies; n and V are fixed.
• With T decreasing, P must decrease to maintain the equation.

Why B is correct:

• Kinetic energy decreases with T (from kinetic theory); pressure decreases proportionally to T (from PV = nRT with constant V and n).

Why the others are wrong:

• A: Pressure decreases, does not increase, as P ∝ T.
• C: Kinetic energy decreases with T, does not stay the same.
• D: Pressure decreases with T, does not stay the same.

Final answer: B