rxrx2004
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why does pv= constant WHEN TEMPERATURE IS CONSTANT?
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CaptainDuckie
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If I’m not mistaken, wouldn’t it be volume is inversely proportional to pressure. Because as you increase volume in a container, the gas pressure would consequently decrease.

Gas pressure is like the colliding particles which causes a force which act at right angles to the walls of the gas container.

Is this GCSE? I recall it from GCSE Physics content.
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rxrx2004
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(Original post by CaptainDuckie)
If I’m not mistaken, wouldn’t it be volume is inversely proportional to pressure. Because as you increase volume in a container, the gas pressure would consequently decrease.

Gas pressure is like the colliding particles which causes a force which act at right angles to the walls of the gas container.

Is this GCSE? I recall it from GCSE Physics content.
it's a level, and it's the same thing. pV=K is the same as p=K/V so yes they are inversely proptional.

but why does temperature have to be constant?
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CaptainDuckie
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(Original post by rxrx2004)
it's a level, and it's the same thing. pV=K is the same as p=K/V so yes they are inversely proptional.

but why does temperature have to be constant?

Well, using my gcse knowledge right...

I recall temperature having an effect on the collision of the particles, so it’s more frequent. I feel likes it because if you increase the temperature, the particles collide more frequently with the walls of the container as they have more kinetic energy. Therefore, the volume would no longer be directly inversely proportional to pressure. So it must be kept constant.

Check your text book?
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rxrx2004
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(Original post by CaptainDuckie)
Well, using my gcse knowledge right...

I recall temperature having an effect on the collision of the particles, so it’s more frequent. I feel likes it because if you increase the temperature, the particles collide more frequently with the walls of the container as they have more kinetic energy. Therefore, the volume would no longer be directly inversely proportional to pressure. So it must be kept constant.

Check your text book?
thanks
it wasn't in my textbook but i remember it now
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Kallisto
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(Original post by rxrx2004)
why does pv= constant WHEN TEMPERATURE IS CONSTANT?
If the volume is constant to the temperature, so the pressure is it too:

p ~ T and V ~ T

becasue it means in turn that the volume depends on the pressure and vice versa, they are indirect proportional to each other: p ~ 1/V. The volume gets reduced the higher the pressure is.

In reference to the particle theory it means that an increasing temperature makes the particles faster to collide with the walls of the container and each other more frequently. An increased pressure would reduced the volume of the container, the frequency of collisions for particles gets higher by increased temperature then.

In a constant volume work (p*V) for a container and a constant temperature, the numbers of collision did not change and that is the meaning in this equation:

p*V = constant, if T = constant.
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CaptainDuckie
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(Original post by Kallisto)
If the volume is constant to the temperature, so the pressure is it too:

p ~ T and V ~ T

becasue it means in turn that the volume depends on the pressure and vice versa, they are indirect proportional to each other: p ~ 1/V. The volume gets reduced the higher the pressure is.

In reference to the particle theory it means that an increasing temperature makes the particles faster to collide with the walls of the container and each other more frequently. An increased pressure would reduced the volume of the container, the frequency of collisions for particles gets higher by increased temperature then.

In a constant volume work (p*V) for a container and a constant temperature, the numbers of collision did not change and that is the meaning in this equation:

p*V = constant, if T = constant.


Out of curiosity, I didn’t do A level physics, can you explain what that means?

As in you increase the number of particles meaning smaller volume? I think you’ve phrased it wrong.
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Joinedup
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The equation applies when you have a fixed number of gas molecules.

e.g. if you seal a fixed mass of gas and therefore a fixed number of gas molecules in a cylinder and change the volume of the gas by pushing a piston into the cylinder that seals against the cylinder sides. if you keep the temperature of the gas constant and you measure the pressure at different volumes what you find is that PV is constant.

what's happening is gas pressure comes from gas molecules having elastic collisions with the sides of the cylinder - higher number of collisions per second means higher pressure

that as the volume of the constant mass of gas is reduced the molecules are packed into less volume and collide with the cylinder walls more frequently.
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Kallisto
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(Original post by CaptainDuckie)
Out of curiosity, I didn’t do A level physics, can you explain what that means?

As in you increase the number of particles meaning smaller volume? I think you’ve phrased it wrong.
It is about a container with a piston: in the container there is a certain (and say constant) number of particles. When I depress the piston, the volume is smaller, the particles have lesser space to move around. IF the temperature is constant, the speed of particles doesn't change, but IF the temperature is increased (not constant!), the speed of particles is faster. In contrast to that, the collision with the walls of the container and the particles themselves is more frequent: there are more particles per unit now (lesser space for the same numbers of gas particles).

In other words: The collision and pressure increases, the volume decreases, the speed of particles is constant (at constant temperature).
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