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Room Temp Winter vs Summer

  1. Jul 11, 2015 #1
    According to KMT, Avarage kinetic energy of 1 mole gas is=(3/2) x R x T
    So , in winter in my cold room ,
    the gases have Kea=34J/mole (T=5oC)

    and in summer that figure climbs to, -roughly- 37J/mole, (T=25oC)
    Difference is , 3J per mole.

    If my rooms dimensions are 3m x 3m x 4m, volume is 36m^3, so
    n is = PV/RT=(1)(36.000)/(0.082)(15+273) (avg temp of 15oC taken to compute number of moles)
    n=1524 mole ==> 3J x 1524= 4573J That's the difference of Energy between winter and summer for my room.

    So, does that mean the air molecules in my room carries 4573J more energy in summer compared to winter?

    How can I put time factor? Can I say they carry that per second?
    Power=E/t=4573/1=4573 Watts??
    Can I assume they hit my body constantly it's as if 4573W heater is in the room and warms me up??
     
  2. jcsd
  3. Jul 11, 2015 #2
    The number of moles is not the same. The room is not a sealed container but one in equilibrium with the atmospheric pressure.
    If you do the calculation right you will see that the total energy is independent of temperature but dependent of pressure.
    Time does not come into the picture.
     
  4. Jul 12, 2015 #3
    Can you elaborate on that pls?
     
  5. Jul 12, 2015 #4
    The number of moles in a room of volume V, at pressure p and temperature T is
    N=pV/RT
    If you multiply this by the energy per mole, u=3/2 RT, the temperature simplifies. There is nothing more to "elaborate".
     
  6. Jul 12, 2015 #5

    Drakkith

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    Staff: Mentor

    No, the energy is not 'per second'. Energy per second would be power, and would imply that the gas is losing or gaining that much energy per second. A gas molecules with X joules of kinetic energy will retain that energy until a collision causes it to either give up or gain energy. As the molecule bounces around over time, it will randomly gain or lose energy with each bounce. If the gas is in equilibrium then all of these collisions tend to cancel themselves out and you can assign an average value.
     
  7. Jul 13, 2015 #6
    Thank you!, you're such a nice person.
     
  8. Jul 13, 2015 #7
    You are welcome. :smile:
     
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