What causes the pressure in a gas?
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Pressure is a force exerted by the substance per unit area on another substance. The pressure of a gas is the force that the gas exerts on the walls of its container. When you blow air into a balloon, the balloon expands because the pressure of air molecules is greater on the inside of the balloon than the outside.
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Gas pressure is caused by the collisions of gas particles with the walls of the container.
Explanation:
According to kinetic theory, molecules inside a volume (e.g. a balloon) are constantly moving around freely.
During this molecular motion, they constantly collide with each other and with the walls of the container.
In a small balloon, that would be many thousands of billions of collisions each second.
The force of impact of a single collision is too small to measure.
However, taken all together, this large number of impacts exerts a considerable force on the surface of the container.
If they hit the surface of the balloon straight on (at a 90 ° angle), they exert their maximum force.
If they hit the surface at an angle less than 90 °, they exert a smaller force.
The sum of all these forces causes the pressure, p, that is exerted by the gas.
The diagram above represents a balloon containing molecules of a gas (the red dots).
The yellow arrows indicate that the gas pressure, p, in the balloon is exerted outward against the walls of the balloon.
The larger the number of collisions per area of the container, the larger the pressure:
Pressure = ForceArea or p=FA.
The direction of this force is always perpendicular to the surface of the container at every point.
Explanation:
According to kinetic theory, molecules inside a volume (e.g. a balloon) are constantly moving around freely.
During this molecular motion, they constantly collide with each other and with the walls of the container.
In a small balloon, that would be many thousands of billions of collisions each second.
The force of impact of a single collision is too small to measure.
However, taken all together, this large number of impacts exerts a considerable force on the surface of the container.
If they hit the surface of the balloon straight on (at a 90 ° angle), they exert their maximum force.
If they hit the surface at an angle less than 90 °, they exert a smaller force.
The sum of all these forces causes the pressure, p, that is exerted by the gas.
The diagram above represents a balloon containing molecules of a gas (the red dots).
The yellow arrows indicate that the gas pressure, p, in the balloon is exerted outward against the walls of the balloon.
The larger the number of collisions per area of the container, the larger the pressure:
Pressure = ForceArea or p=FA.
The direction of this force is always perpendicular to the surface of the container at every point.
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