- #1
mrandersdk
- 246
- 1
Hello
I got to thinking about temperature when i prepared a lecture for my high school class. For a monoatomic ideal gas the temperature is proportional with the average kinetic energy of the atoms. For a diatomc gas we also have rotational energy (vibrations assumed to be freezed out), and for a polyatomic gas we have kinetic, rotational and vibrational energy. For a solid we have vibrational energy.
Lets assume we take a solid and a monoatomic gas and put into contact, and they reach thermal equilibrium. The monoatomic gas will have an average energy per atom of [tex] \frac{3}{2}k_b T [/tex] and the solid would have an average energy per atom of [tex] \frac{6}{2}k_b T =3 k_b T[/tex] (in the classical limit).
The gas and solid being in thermal equilibrium will have the same temperature. If we take the simple definition of temperature, that two objects have the same temperature if there is no net energy transfer between them, there is something I can't rap my head around:
Why will the solid not transfer its energy to the gas, when it has a higher average energy? I know I'm probably just forgetting some simple fact, but I just can't seem to figure it out somehow. It has never troubled me before, but when you teach, you suddenly stumble across things you thought was logical, but when you really look at it, it may not be.
Anybody that can help me with a simple picture, that can help me see this i logical (preferable a explanation high school student would appreciate too, but any help is appreciated)
Thanks in advance
Anders
I got to thinking about temperature when i prepared a lecture for my high school class. For a monoatomic ideal gas the temperature is proportional with the average kinetic energy of the atoms. For a diatomc gas we also have rotational energy (vibrations assumed to be freezed out), and for a polyatomic gas we have kinetic, rotational and vibrational energy. For a solid we have vibrational energy.
Lets assume we take a solid and a monoatomic gas and put into contact, and they reach thermal equilibrium. The monoatomic gas will have an average energy per atom of [tex] \frac{3}{2}k_b T [/tex] and the solid would have an average energy per atom of [tex] \frac{6}{2}k_b T =3 k_b T[/tex] (in the classical limit).
The gas and solid being in thermal equilibrium will have the same temperature. If we take the simple definition of temperature, that two objects have the same temperature if there is no net energy transfer between them, there is something I can't rap my head around:
Why will the solid not transfer its energy to the gas, when it has a higher average energy? I know I'm probably just forgetting some simple fact, but I just can't seem to figure it out somehow. It has never troubled me before, but when you teach, you suddenly stumble across things you thought was logical, but when you really look at it, it may not be.
Anybody that can help me with a simple picture, that can help me see this i logical (preferable a explanation high school student would appreciate too, but any help is appreciated)
Thanks in advance
Anders