How Does Room Temperature Affect Air Molecule Energy from Winter to Summer?

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Discussion Overview

The discussion centers on how room temperature affects the energy of air molecules, specifically comparing winter and summer conditions. It involves concepts from kinetic molecular theory (KMT) and explores calculations related to kinetic energy, number of moles, and the implications of these factors on perceived warmth in a room.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant calculates the average kinetic energy of air molecules in winter and summer, concluding a difference of 4573J in energy due to temperature changes.
  • Another participant challenges the assumption that the number of moles remains constant, stating that the room is not a sealed container and that total energy is independent of temperature but dependent on pressure.
  • A further reply emphasizes that energy is not a measure of power and explains that gas molecules retain energy until collisions alter their energy state.
  • Some participants reiterate the formula for calculating the number of moles and energy per mole, indicating that temperature simplifies in the calculations.

Areas of Agreement / Disagreement

Participants express disagreement regarding the assumptions about the number of moles and the interpretation of energy as power. The discussion remains unresolved as different viewpoints are presented without consensus.

Contextual Notes

Limitations include the assumption of a sealed system versus an open one, the role of pressure in determining energy, and the interpretation of energy in terms of power over time.

skepticwulf
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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??
 
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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.
 
Can you elaborate on that pls?
 
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".
 
skepticwulf said:
Can I say they carry that per second?

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.
 
nasu said:
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".
Thank you!, you're such a nice person.
 
You are welcome. :smile:
 

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