Question

Why does a gas exert pressure on the walls of its container? Explain using kinetic theory.

When an automobile travels for a long distance the air pressure in the tyres increases. Why?

A balloon is filled with helium gas and sealed at room temperature (300 K). It is then placed in sunlight, and the gas inside gets heated. The balloon is flexible and can expand to accommodate the increased pressure. A science student observes that as the temperature increases, the balloon expands and rises higher in the air. The student wants to understand this behavior using the kinetic theory of gases. According to this theory, gas molecules are in continuous random motion, colliding with each other and the container walls. These collisions are responsible for exerting pressure.

A gas is enclosed in a frictionless piston-cylinder arrangement. Initially, the gas is at room temperature and atmospheric pressure. The piston is slowly pushed inward, compressing the gas isothermally (temperature remains constant). As the gas is compressed, the volume decreases, and the pressure increases. The student performing this experiment refers to the kinetic theory of gases to understand the molecular explanation behind the increase in pressure.