Perfect gasses temperature vs kinetic energy per molecule

In summary, the conversation discusses the relationship between temperature and kinetic energy, specifically in regards to the perfect gas law. The conclusion is that the kinetic energy per molecule is equal to 3/2 times the product of pressure and volume divided by the number of molecules. This is due to the three modes of motion that contribute to the kinetic energy of a molecule.
  • #1
madah12
326
1

Homework Statement


I have been wondering about temperature and it's relation to kinetic energy I didn't study thermodynamics so I hope that replies could be simplified.I am trying to think about the perfect gas law to relate kinetic energy per molecule to temperature, and I want to know if I have a somewhat close understanding.


Homework Equations


PV=RnT


The Attempt at a Solution


PV=RnT
I am thinking that P*V expresses the energy stored in the gas molecules since P =F/A and V=m^3 so P*V=F*m which is the unit of work so W=RnT
and since the work expresses the change of kinetic energy
deltaK= RnT
(delta K)/n = RT
so this gives me the intuition that since the change of kinetic energy per molecule is equal to a constant times the temperature so its proportional to it. I didn't study thermodynamics and only basics of physical chemistry so probably there are things I missed but is my intuition at least correct?
 
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  • #2
Your intuition (or subconsciously-remembered info) is in the right direction
... but the PV is related to the Work that can be done on the Area (2-d),
not the entire molecule KE , which comes from motion in all 3 dimensions.
So, the KE per molecule (an average, of course) is actually 3/2 * PV/n .
... this is translational KE of the molecule's center-of-mass, not including
rotational KE and vibrational KE of the atoms relative to that c.o.m.

It is more traditional to write KE = 3/2 N kT , with N being the number of molecules,
and k is Boltzmann's konstant = 1.38E-23 J/K , which is R/N_avagadro .
The "3" signifies that there are 3 modes of motion which contribute to this KE ; every mode (including means rotations and vibrations also, if they occur) in a molecule holds E(average) = 1/2 kT .
 

What is the relationship between the temperature of a perfect gas and the kinetic energy per molecule?

The temperature of a perfect gas and the kinetic energy per molecule are directly proportional. This means that as the temperature of the gas increases, the kinetic energy per molecule also increases. Similarly, as the temperature decreases, the kinetic energy per molecule decreases.

How does the kinetic energy of a molecule in a perfect gas relate to its speed?

The kinetic energy of a molecule in a perfect gas is directly related to its speed. This means that as the kinetic energy increases, the speed of the molecule also increases. Conversely, as the kinetic energy decreases, the speed of the molecule decreases.

How does the temperature of a perfect gas affect the average kinetic energy per molecule?

The temperature of a perfect gas is directly related to the average kinetic energy per molecule. As the temperature increases, the average kinetic energy per molecule also increases. This is because an increase in temperature means that the molecules in the gas are moving faster and have higher kinetic energy.

Is the relationship between temperature and kinetic energy per molecule the same for all gases?

No, the relationship between temperature and kinetic energy per molecule may vary for different gases. This is because the properties of a gas, such as its molecular weight and intermolecular forces, can affect the relationship between temperature and kinetic energy per molecule.

How does the kinetic energy per molecule of a perfect gas change with changes in temperature?

The kinetic energy per molecule of a perfect gas increases with an increase in temperature and decreases with a decrease in temperature. This is because temperature is a measure of the average kinetic energy of the gas molecules, so any change in temperature will result in a corresponding change in the average kinetic energy per molecule.

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