### Author Topic: Molecular Model for an Ideal Gas  (Read 497527 times)

#### lookang

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##### Re: Molecular Model for an Ideal Gas
« Reply #15 on: April 12, 2008, 10:57:17 am »
thanks!!

#### anaktyl

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• Posts: 3
##### Re: Molecular Model for an Ideal Gas
« Reply #16 on: January 08, 2009, 10:01:28 pm »
hi Prof

I'm not programmer but chemist,and I have a favour ,Do you have any applet similar above but with constant volume and change mass of particles-choose one of ideal gases.

Thank you very much for help
« Last Edit: January 08, 2009, 10:06:31 pm by anaktyl »

#### Fu-Kwun Hwang

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##### Re: Molecular Model for an Ideal Gas
« Reply #17 on: January 09, 2009, 06:48:58 pm »
Parameters for ideal gas are Pressure P, Volume V, number of particles N and Temperature T.

P*V=N*R*T

You want volume to be kept the same, and change the mass of the particles (different gas).
What else need to be the same? or changed?

If it is the same temperature T and the same number of particles, then pressure will be the same.
Because the same temperature T, means the same average kinetic energy.
So heavy particles will have less average velocity (compared to light particles).

#### anaktyl

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##### Re: Molecular Model for an Ideal Gas
« Reply #18 on: January 09, 2009, 10:33:11 pm »
Hi Prof

Yes I agree with you. PV=NRT

but If we change the volume the pressure will be going up or down P=NRT/V and  the particles will be moving slower or faster, it's similar with changing mass of particles

So I just need very simple animation, where can I change just number of particles, ideal gas(mass of particles), and volume.

Thank you for help

#### Fu-Kwun Hwang

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##### Re: Molecular Model for an Ideal Gas
« Reply #19 on: January 10, 2009, 12:09:51 pm »
What do you mean by change just number of particles, ideal gas(mass of particles), and volume.
Do you mean change all of the above 3 patrameter at the same time and without changing other parameters?

From P*V=N*R*T:
If you can freely change V and N, there is no way to keep P and T constant (unless V/N is keep as constant,too!)

When you use mouse to change parameters, you can adjust one parameter at a time.
Let me know exactly what you want to do. Please give me an example (in detail) and I will try to find way to help you! O.K.?

#### anaktyl

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##### Re: Molecular Model for an Ideal Gas
« Reply #20 on: January 19, 2009, 04:52:10 am »
Hi

for example on the top you showing how the volume is moving along with pressure (up,down),
I need the animation where volume is constant means you can change using mouse or tape the size, and then tape the number of molecules, and showing how pressure is changing, it makes sense

#### Fu-Kwun Hwang

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##### Re: Molecular Model for an Ideal Gas
« Reply #21 on: January 19, 2009, 10:31:02 am »
Registed user can get files related to this applet for offline access.
Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list

The above simulation was designed for a system with piston so that the volume changed according to external apply modification: change pressure, temperature or number of particles.

I modified another simulation to simulate what you want.
You can select Volume fixed checkbox, then you can change number of particle,temperature and the pressure will change according to your input (you can also change volume,too!).

Registed user can get files related to this applet for offline access.
Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list

#### descale

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• Posts: 2
##### Re: Molecular Model for an Ideal Gas
« Reply #22 on: March 01, 2009, 08:49:32 am »
Hello,
this Java Applet is excellent, perfect work! I have few a questions. Can you help me, please?

1) Why are there used Runge Kutta equations?
2) How to calculate the accuracy of volume calculation?
3) Can we find there method Monte Carlo?
4) It is there momentum?

Thank you very much. Tomas

#### Fu-Kwun Hwang

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##### Re: Molecular Model for an Ideal Gas
« Reply #23 on: March 01, 2009, 09:12:49 am »
1.If the volume is fixed and without consider gravitation effect, you do not need to use Runge-Kutta method.
2. I do not understand the rest of your questions:
Quote
2) How to calculate the accuracy of volume calculation?
3) Can we find there method Monte Carlo?
4) It is there momentum?
e.g. what do you mean by "the accuracy of volume calculation"?
Why you want to find  Monte Carlo method?
momentum??? DO you maen "linear momentum"?

#### descale

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• Posts: 2
##### Re: Molecular Model for an Ideal Gas
« Reply #24 on: March 01, 2009, 10:10:09 am »
e.g. what do you mean by "the accuracy of volume calculation"?
Why you want to find  Monte Carlo method?

I thought there has been applied method Monte Carlo. And the accuracy of Monte Carlo is 1/sqr(n). That's okay, thank you.

#### Fu-Kwun Hwang

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##### Re: Molecular Model for an Ideal Gas
« Reply #25 on: March 01, 2009, 12:05:05 pm »
The volume of the system was calculated from width/height and display the average( in time).

#### siuchun

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• Posts: 2
##### Re: Molecular Model for an Ideal Gas
« Reply #26 on: April 06, 2009, 10:23:15 pm »
Dear Prof Hwang,

I have learned your molecular model for an ideal gas in the internet. It's a fantastic simulation.

Now I have a question that if the collision between the partials and walls is not elastic, the wall will occur plastic deformation after collision. Can this model be used to simulate the phenomenon?

#### Fu-Kwun Hwang

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##### Re: Molecular Model for an Ideal Gas
« Reply #27 on: April 07, 2009, 09:11:40 am »
You need to define the model for your case:
How the wall will be deformed and how much enegy will be loss duing collision and what that will affect later collision.

It will be easier to modify it from EJS version of ideal gas law: PV=nRT

#### siuchun

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• Posts: 2
##### Re: Molecular Model for an Ideal Gas
« Reply #28 on: April 07, 2009, 11:08:07 am »
In fact, I am not familiar with Java. Can I simulate that plastic collision in MATLAB?
« Last Edit: April 07, 2009, 11:26:19 am by siuchun »