Kinetic Molecular Theory Explains Gas Behavior at Constant Volume

Steps:

• Heating air increases its internal energy, raising the average kinetic energy of molecules.
• At constant volume, the container size doesn't change, so molecules can't spread out more.
• Higher kinetic energy means molecules move faster on average.
• Faster molecules collide with container walls more often, increasing pressure.

Why C is correct:

• According to the kinetic theory, pressure is proportional to the frequency of wall collisions times molecular momentum; temperature rise boosts speed, thus collision frequency (from ideal gas law PV = nRT, where P increases as T rises at fixed V and n).

Why the others are wrong:

• A: Molecules don't expand; they are point masses in kinetic theory, and heating only increases their speed.
• B: Collisions between molecules increase, but the question focuses on overall heating effect; wall collisions directly relate to pressure.
• D: Sealed container means constant number of molecules (n fixed in ideal gas law).

Final answer: C