Notices
Results 1 to 10 of 10
Like Tree2Likes
  • 1 Post By tk421
  • 1 Post By tk421

Thread: Absolute zero

  1. #1 Absolute zero 
    New Member
    Join Date
    Jun 2013
    Posts
    1
    I'm currently studying for my IGCSE is physics and my syllabus often oversimplifies things, so they no longer make any sense.

    In my textbook it states that: "As a gas is cooled (if kept at a constant volume), the pressure keeps decreasing. However, the pressure of a gas cannot become less that zero. The temperature in which the gas cannot be cooled anymore is known as absolute zero (-273 degrees Celcius)"
    I would imagine that at these tempertures, gases would freeze, yet my textbook implies that the gases never freeze.
    Is this a misunderstanding on my part? Or has the textbook oversimplified?

    Thanks


    Reply With Quote  
     

  2.  
     

  3. #2  
    New Member
    Join Date
    Jun 2013
    Posts
    2
    High temperature in a gas makes the molecules shake alot and creates a certain amount of pressure, as the temperature lowers, less energy is put into the molecules which causes that they shake less, and collide less, which causes that the pressure drops. At a certain temperature (0 Kelvin = -273,15 C) the temperature can't be lower anymore, and there is no energy putt in the molecules which causes that they doesn't shake anymore and doesn't collide, and so their isn't any pressure anymore. However, nobody achieved to drop the temperature of a gas lower than -273C so it is pretty much impossible to reach the absolute zero.
    It is possible to keep a gas from freezing as the pressure is kept low.
    I hope you understand as my engish is pretty bad, search for 'phase transition' on wikipedia, it shoud help you alot!


    Reply With Quote  
     

  4. #3  
    Forum Masters Degree MrMojo1's Avatar
    Join Date
    Mar 2012
    Location
    South Florida, USA
    Posts
    618
    I've understood that absolute zero is at best a concept, since atoms are always vibrating. I this interesting article below, which defined absolute zero is:

    Absolute zero corresponds to the theoretical state in which particles have no energy at all, and higher temperatures correspond to higher average energies.
    Perhaps a physicist can give you a more thorough explanation.

    Quantum gas goes below absolute zero
    Reply With Quote  
     

  5. #4  
    Forum Freshman snak's Avatar
    Join Date
    Jun 2013
    Location
    Lisboa, Portugal
    Posts
    6
    does helium ever reach a solid state?
    Or is superfluid the end of the line?
    Reply With Quote  
     

  6. #5  
    Anti-Crank AlexG's Avatar
    Join Date
    Mar 2012
    Posts
    2,809
    At normal pressure, helium remains a fluid down to absolute zero. Solid helium requires a temperature of 1–1.5 K (about −272 C or −457 F) and about 25 bar (2.5 MPa) of pressure.
    Its the way nature is!
    If you dont like it, go somewhere else....
    To another universe, where the rules are simpler
    Philosophically more pleasing, more psychologically easy
    Prof Richard Feynman (1979) .....

    Das ist nicht nur nicht richtig, es ist nicht einmal falsch!"
    Reply With Quote  
     

  7. #6  
    Forum Freshman snak's Avatar
    Join Date
    Jun 2013
    Location
    Lisboa, Portugal
    Posts
    6
    thanks
    Reply With Quote  
     

  8. #7  
    Suspended
    Join Date
    Dec 2011
    Location
    I live in Los Angeles but travel a lot and spend some time in Mexico.
    Posts
    1,509
    As present definitions go, absolute zero means that there is no energy within a system/ physical volume/ atom/ molecule(s). There have been claims of lower "temperatures" than absolute zero. Whether this is true or not is partly based upon definitions. If temperatures were possible below absolute zero then such a volume would always draw energy from its environment, as any temperature would if its surrounding environment were at a higher temperature. Here is an explanation of it.

    A temperature below absolute zero
    Reply With Quote  
     

  9. #8  
    Forum Isotope
    Join Date
    Feb 2012
    Location
    Western US
    Posts
    2,933
    Quote Originally Posted by forrest noble View Post
    As present definitions go, absolute zero means that there is no energy within a system/ physical volume/ atom/ molecule(s).
    Sigh. True to form, Forrest, you mangle the definition. Can you PLEASE refrain from providing answers when you don't know what you're talking about? If you can't, then at least cut-and-paste from an authoritative source. Stop relying on pop-sci press articles. But it would be best if you merely stopped answering until you actually learn the material. You create extra work for those of us who care enough to mop up after you make a mess.

    Absolute zero is formally defined as the temperature at which the change in entropy -- not energy -- goes to zero, so that the entropy is a minimum. There remains at that temperature the zero-point energy. Given how many times you've blathered incessantly about ZPE, it's somewhat of a surprise that you understand it so poorly that you fail to mention it in your "answer" here. But only somewhat.
    Last edited by tk421; June 12th, 2013 at 05:47 PM. Reason: ETA: Corrected "entropy" to "change in entropy" and added clause re: minimum entropy. Thanks, exchemist!
    PhDemon likes this.
    Reply With Quote  
     

  10. #9  
    exchemist
    Join Date
    May 2013
    Location
    London
    Posts
    3,683
    Quote Originally Posted by tk421 View Post
    Quote Originally Posted by forrest noble View Post
    As present definitions go, absolute zero means that there is no energy within a system/ physical volume/ atom/ molecule(s).


    Absolute zero is formally defined as the temperature at which entropy -- not energy -- goes to zero. There remains at that temperature the zero-point energy. .
    I'm rusty on all this but just a quibble: if Entropy is Q/T, then isn't it a bit tautologous to define absolute zero as the temperature at which entropy goes to zero?
    Reply With Quote  
     

  11. #10  
    Forum Isotope
    Join Date
    Feb 2012
    Location
    Western US
    Posts
    2,933
    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by tk421 View Post
    Quote Originally Posted by forrest noble View Post
    As present definitions go, absolute zero means that there is no energy within a system/ physical volume/ atom/ molecule(s).


    Absolute zero is formally defined as the temperature at which entropy -- not energy -- goes to zero. There remains at that temperature the zero-point energy. .
    I'm rusty on all this but just a quibble: if Entropy is Q/T, then isn't it a bit tautologous to define absolute zero as the temperature at which entropy goes to zero?
    You're not a bit rusty at all! In my haste, I omitted an all-important delta. I've corrected my post to read "change in entropy." Thanks for your eagle eyes!
    Neverfly likes this.
    Reply With Quote  
     

Similar Threads

  1. Absolute Zero & Absolute Hot
    By arKane in forum Physics
    Replies: 6
    Last Post: December 7th, 2012, 03:09 PM
  2. absolute temperature vs absolute pressure!
    By precious in forum Chemistry
    Replies: 4
    Last Post: November 10th, 2011, 04:27 AM
  3. about the absolute zero ???
    By Ahmed gamal in forum Physics
    Replies: 8
    Last Post: February 27th, 2010, 04:52 PM
  4. Absolute Zero
    By leohopkins in forum Chemistry
    Replies: 12
    Last Post: February 6th, 2007, 03:20 PM
  5. Absolute Zero
    By thevignesh in forum Chemistry
    Replies: 25
    Last Post: August 1st, 2006, 07:02 PM
Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •