Understanding Gas Energy States: A Quantum Physics Analysis

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In summary: So, in the long run, the entropy would be higher for a system in equilibrium than for one that's not in equilibrium.In summary, most of the energy states in a gas are empty because the principle quantum number (which is a variable of the energy eigenvalue) is any positive integer from 1 to infinity. This is valid for all gases, though ideal gases only have a finite number of energy states.
  • #1
spaghetti3451
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For gases at room temperature and pressure, at a given time, why are most of the energy states empty? (I am analysing the situation using the principles of quantum physics, i.e. wavefunctions, quantum states, etc.) Is this valid for all gases? Are we dealing with ideal gases only?
 
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Because there's an infinite number of states?
 
  • #3
Please confirm if I am correct on the following:

According to the principles of classical physics, the number of energy states would be infinite becuase energy is a continuous variable. Am I right?

And, according to the principles of quantum physics, the number of energy states would also be infinite because the principal quantum number (which is a variable of the energy eigenvalue) is any positive integer from 1 to infinity. Am I right? I believe this is what you were referring to through your reply.

If I am right, I would then like to ask this question:

Even if there is an infinite number of energy states, why do most of the energy states have to be empty? For instance, the probability distribution for the occupancy of particles might be skewed to one end.

And in the case of a flat probability distribution, the curve should be zero, shouldn't it?
 
  • #4
failexam said:
According to the principles of classical physics, the number of energy states would be infinite becuase energy is a continuous variable. Am I right?

And, according to the principles of quantum physics, the number of energy states would also be infinite because the principal quantum number (which is a variable of the energy eigenvalue) is any positive integer from 1 to infinity. Am I right? I believe this is what you were referring to through your reply.

Well, you have an infinite number of bound states for a particle in a potential well, but you also have a continuum of states for a free particle. A free particle can, after all, have any kinetic energy, even in QM. So, the kinetic energy of your gas particles is continuous, to begin with.
Even if there is an infinite number of energy states, why do most of the energy states have to be empty? For instance, the probability distribution for the occupancy of particles might be skewed to one end.

Well, you have a finite amount of energy to distribute. In equilibrium, it'd be distributed as the Boltzmann distribution. If the energy has some other 'uneven' distribution, then you're not in equilibrium. The energy will (eventually) redistribute itself, lowering the entropy. The entropy of a system is essentially a measure of the distribution of energy, which is an irreversible process. A rod that's been heated at one end will have its temperature even out eventually, but rod at thermal equilibrium won't spontaneously become hotter at one end. (Or more specifically, not to the extent that any work could be extracted from that. AKA "Maxwell's demon")
 
  • #5
alxm said:
you have an infinite number of bound states for a particle in a potential well,

Does a particle have kinetic energy inside a potential well? What is the value of its potential energy inside the well?

alxm said:
but you also have a continuum of states for a free particle.

I guess, because you have a continuum of states for a free particle in the special case of zero potential, the gap between energy levels drops in some arbitrary manner with decreasing potential?

alxm said:
A free particle can, after all, have any kinetic energy, even in QM.

But the kinetic energy can't be negative, even in QM, right?

alxm said:
So, the kinetic energy of your gas particles is continuous, to begin with.

But that's when the particle is free. What about the more complex case of a classical gaseous particle in some arbitrary potential?

alxm said:
Well, you have a finite amount of energy to distribute. In equilibrium, it'd be distributed as the Boltzmann distribution.

Shouldn't we say Fermi-Dirac/ Bose-Einstein distribution as we are dealing in energy levels and therefore analysing in the quantum world?

alxm said:
If the energy has some other 'uneven' distribution, then you're not in equilibrium.

By 'uneven', do you mean a curve that deviates from the Boltzmann distribution?

alxm said:
The energy will (eventually) redistribute itself, lowering the entropy.

But as far as I know, the entropy of any system increases.
 

FAQ: Understanding Gas Energy States: A Quantum Physics Analysis

What is the concept of gas energy states?

Gas energy states refer to the specific energy levels that a gas molecule can have. These energy levels are quantized, meaning they can only exist at certain discrete values. In other words, a gas molecule can only have a certain amount of energy and cannot have any value in between those levels.

How is quantum physics used to analyze gas energy states?

Quantum physics is used to analyze gas energy states by providing a framework for understanding the discrete energy levels of gas molecules. This includes principles such as quantization, uncertainty, and wave-particle duality. The Schrodinger equation is also used to calculate the allowed energy states of gas molecules.

What are the factors that affect gas energy states?

There are several factors that can affect gas energy states. These include the temperature, pressure, and composition of the gas. Changes in these variables can cause the gas molecules to gain or lose energy, resulting in different energy states. External factors such as electromagnetic fields can also influence gas energy states.

How do gas energy states relate to the behavior of gas molecules?

The energy states of gas molecules directly impact their behavior. At higher energy states, gas molecules tend to move faster and collide more frequently, resulting in higher pressure. At lower energy states, gas molecules move slower and have less frequent collisions, resulting in lower pressure. Gas energy states also influence other properties such as heat capacity and thermal conductivity.

Why is understanding gas energy states important in practical applications?

Understanding gas energy states is crucial in many practical applications, such as in the design and operation of engines, refrigeration systems, and chemical reactions. It also plays a role in understanding the behavior of gases in different environments, such as in outer space. Understanding gas energy states can also lead to the development of new technologies and materials that utilize the unique properties of gas molecules at specific energy states.

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