Final answer:
Pressure is caused by the collisions of gas molecules with each other and with their container. This creates a force that results in pressure.
Step-by-step explanation:
Pressure is caused by the collisions of gas molecules with other gas molecules and with their container. When gas molecules collide, they exert a force due to their momentum, resulting in pressure. This can be demonstrated with the example of a gas in a container. As the gas molecules collide with the walls of the container, they create pressure on the walls.
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