1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Thermodynamics & Thermal Energy

  1. Dec 9, 2007 #1
    (SOLVED)Thermodynamics & Thermal Energy

    1. The problem statement, all variables and given/known data
    a 6.0m X 8m X 3m room contains air at 20 Degrees Celcius

    2. Relevant equations
    What is the room's thermal energy

    3. The attempt at a solution

    now i know that oxygen is a diatomic atom so i used

    E(thermal)= 5/2 NkbT= 5/2 nRT

    i tried to find the amount of moles by doing pv=nrt -> 5/2 pv=5/2 nRT but i don't know either the pressure exerted neither the number of moles

    so i was think to find pV i could use pV= 2/3N*[tex](\epsilon)[/tex](Average Translational kinetic energy)
    where [tex](\epsilon)[/tex]= 3/2 KbT

    so i have one question would it work like that?
    Last edited: Dec 9, 2007
  2. jcsd
  3. Dec 9, 2007 #2
    any info or help is appreciated, anything cause i have no idea if that process is right
  4. Dec 9, 2007 #3
    I am not sure, but I believe you could find n by using the volume of the room and the fact that it is at 20 Celsius.

    That is since density=mass/volume.

    I am just guessing though.

  5. Dec 9, 2007 #4

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    Use n = PV/RT to find the number of moles. Then use:

    [tex]U = \frac{5}{2}nRT[/tex] where T = temperature in Kelvins, to find the total internal energy of the air.

    This, of course, assumes it is a perfect ideal gas so that the heat capacity of the air is 5R/2 at all temperatures which is not true.

    Last edited: Dec 9, 2007
  6. Dec 9, 2007 #5
    yeah i took a look at that but because the temperature is higher than STP i don't know density or mass
  7. Dec 9, 2007 #6

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    You are supposed to assume that it is at atmospheric pressure. It is a room in a building, not a sealed chamber.

  8. Dec 9, 2007 #7
    WOW thanks this really helped me i didn't knew that the temperature didn't affect the atmospheric pressure, i solved it thanks
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Thermodynamics & Thermal Energy
  1. Thermal energy. (Replies: 5)

  2. Thermal Energy (Replies: 1)