According to the kinetic theory of gases, the pressure exerted by a gas on the walls of its container is directly caused by:
the gravitational attraction between the gas molecules and the container walls.
the rate of change of momentum of the gas molecules as they collide with and rebound from the walls.
the loss of kinetic energy of the gas molecules during elastic collisions.
the collisions between the gas molecules themselves within the volume of the container.
321 exam-style questions on CIE IGCSE Physics 2.1 Kinetic particle model of matter, covering 2.1.1 States of matter and changes of state, 2.1.2a Particle structure and motion in solids, liquids and gases, 2.1.2b Gas pressure and particle collisions, 2.1.2c Brownian motion, 2.1.3a The absolute scale of temperature, and 2.1.3b Pressure, volume and temperature of a gas. Each one has a worked solution and a mark scheme showing where the marks go.