A pressurized perfume bottle is left on the window pane of a room. What happens to he gas molecules of the perfume on a sunny day? They

Analyze the question: A pressurized perfume bottle sits on a window pane in the sun. The sunlight heats the bottle and the gas inside. We need to say what happens to the gas molecules.

Concept (Kinetic Theory of Gases):

• Temperature is a measure of the average kinetic energy of the molecules.
• When a gas is heated, its molecules gain kinetic energy, so they move faster.
• Faster molecules collide with each other and with the container walls more often and with greater force. This raises the pressure (Pressure Law: P ∝ T at constant volume).

Solution:

1. Sunlight warms the window pane and the bottle, so the temperature of the gas rises.
2. Higher temperature means higher average kinetic energy of the molecules, so they move more rapidly.

Checking each option:

• A. Expand: The molecules themselves do not expand. The gas could expand only if the container allowed it, and a rigid bottle does not.
• B. Collide less often: Wrong. Faster molecules collide more often.
• C. Move more rapidly: Correct. This follows directly from the increase in kinetic energy.
• D. Contract: Wrong. Heating does not make the gas contract.

Answer: C. They move more rapidly.

Tip: In kinetic theory questions, link heat → temperature ↑ → kinetic energy ↑ → speed ↑. Individual molecules never expand or contract. Only the spacing and motion of the molecules change.