Physics for IGCSE & O level - Thermal Effects (Section 1 - No. 31)
Why does a gas exert pressure on the walls of its container?
Because the gas molecules are tightly packed.
Because the gas molecules are not moving.
Because the gas molecules are colliding with the walls.
Because the gas molecules are repelling each other.
Explanation
Gas molecules exert pressure when they collide with the container walls.