Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: How can I answer them?

  1. Nov 25, 2007 #1

    I have some question i hope i can fine the answer here:

    1) is it possible for two bodies to be in thermal equilibrium without being in physical contact?explain

    2)an ideal gas expands to twice its volume under isothermal and adiabatic conditions. in which case is the final temperature the highest? in which case is the change in internal energy greatest?

    3)an aluminium foil has one shiny surface and one dull surface. how would you wrap the potato to bake it efficiently? explain

    4)how much heat is needed to convert 80g of ice initially at-10 C to 60g of water and 20g of steam at 100 C?

    specific heat capacity of ice=2100 JKg-1K-1, specific heat capacity of water= 4190 JKg-1K-1, latent heat of fusion of ice=334 kJkg-1, latent heat of vapourisation of water=2260 kJkg-1

    thanx in advance
    Last edited: Nov 25, 2007
  2. jcsd
  3. Nov 25, 2007 #2


    User Avatar
    Science Advisor
    Homework Helper

    Welcome to PF beterban.

    I'm not going to give you the answers, but make you think yourself :tongue:
    But here are some hints:
    In 1): Suppose two bodies are not in equilibrium. What would have to be transferred to establish equilibrium? Is it something for which physical contact is needed or not?
    For 2) you can use the ideal gas law. Can you quote it?
    Your intuition may even help you in 3): one of the sides will reflect the heat, the other will absorb it... which side is which do you think?
    For 4) you will need to do something with the heat capacity. What is the heat capacity and how can you use it?
  4. Nov 25, 2007 #3
    For what it's worth, #3 is one of the great folk myths. For ordinary aluminum foil, it makes no discernible difference. If the aluminum foil is the non-stick kind, shiny side goes out.
    http://www.alcoa.com/reynoldskitchens/en/faq_detail.asp?info_page_id=743&prod_id=1789&cat_id=1337 [Broken]
    Last edited by a moderator: May 3, 2017
  5. Nov 25, 2007 #4
    :rolleyes: you know..!!!

    When i think about it i will find that it is possible if the mass,material (specific heat) & surrounding temperature not be in thermal equilibrium

    am I correct?
  6. Nov 25, 2007 #5
    sorry but why you dont ?

    and thanx to TVP45 for the information which he has been provided
    Last edited: Nov 25, 2007
  7. Nov 26, 2007 #6
    I think there aren't enough knowledge in this forum,those is easy question but I'm not sure from some and didn't understand the other some what sould i do than?

    I hope this useful to get help

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook