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Can a pencil be put back together

  1. May 15, 2006 #1
    A friend of mine was asking the teacher, why can't a pencil ( or any object for that matter) just simply..be put together if it's snapped in half. Are bonds broken, whats going on here? What's causing me from connecting the two pieces back together back to its original form without a catalyst such a glue.... This question is on the atomic or subatomic level, peers where saying " because the wood and graphite is seperated" thats true in a sence, but i want to go atomic.
  2. jcsd
  3. May 15, 2006 #2
    Im no chemist, but there is probably an energy barrier that must be overcome before the bonds will re-establish themselves. In order to get over this energy barrier, you will need to supply some sort of energy input to do this. If this were not true, then you would be able to put broken pencils back together again and see a net amount of energy released as the bonds are made. Remember, chemical bonds are either exothermic or endothermic. You can't simply just "make bonds" without taking energy into consideration.
  4. May 15, 2006 #3
    But this is no chemical change it's a physical change correct?
  5. May 15, 2006 #4


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    One of the things that happens, though by no means the only factor, is that any "loose ends" will immediately be surrounded by oxygen and begin oxydizing. Same with hydorgen. AQlmost instantly, the edges are not volatile.

    Then again, this would suggest that, in a vacuum we wouldn't have that problem...
  6. May 15, 2006 #5
    Incorrect, you must re-make chemical bonds with the pencils carbon and graphite atoms for it to become 'unbroken'

    Edit: It has been a while since I took Chemistry. In a sense, yes it is physical because the chemical properties of the pencil are the same.
    Last edited: May 15, 2006
  7. May 15, 2006 #6


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    It would also suggest that inert materials like platinum or materials that are already oxides such as SiO2, would not have this problem. (But like you said there could be other factors as well) I once asked this question and someone told me that the air physically obstructs the re-formation of the bonds. Again this would suggest that in a vacuum, you could simply stick solids back together. I don't know if this is true.
  8. May 15, 2006 #7
    Oh, i was talking about the seperating, of the carbon and graphite atoms.

    And dave, why doesnt the pencil in whole.. just oxidize it's? I understand what your saying, by seperating the pencil.. the " loose ends" will oxydize.
  9. May 15, 2006 #8
    What do you mean,


    I just explained why.
  10. May 15, 2006 #9
    Theoretically, in a vacuum it's possible..

    but if air obstructs the reformation of bonds, wouldn't it also obstruct the formation of bonds? The pencil doesn't occur naturally.. is that were you going? Are you saying, the bonds are seperate for " the wood" and the "graphite". And there just combined by pressure to make the pencil, and when the pencil is broken, it can't be put together because of the seperate bonds?

    I thought it delt with antimatter and matter ordinances.. but im probably wrong.
  11. May 15, 2006 #10


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    Yes, but it seems likely that the same mechanism is responsible for preventing all solids from sticking together, rather than millions of different mechanisms for different solids that all have the same effect.
  12. May 15, 2006 #11
    Am I speaking Chinese?
  13. May 15, 2006 #12


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    Yeah, I don't think there is any chemical bond between the wood and graphite in a pencil, but I'm not saying the air thing is correct, I'm just saying that's how someone explained it to me, but it never sat well with me.
  14. May 15, 2006 #13
    This is a science forum. Leave the crackpotery out of it, please. :mad:
  15. May 15, 2006 #14
    I understand you have to "remake the bonds"

    but what are the bonds?

    You answer my question, im just lookin for a more in depth answer

    is it the " equilibrium" concept?
    Last edited: May 15, 2006
  16. May 15, 2006 #15


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    What do you mean?
  17. May 15, 2006 #16
    The bond's are whatever holds the atoms together, Colvalent or Ionic or Vander-walls.

    What do you mean nothing is lost but the "miniscule loose edges?" Where are you getting this bad science from?
  18. May 15, 2006 #17
    It is a physical change right? I understand how it could be a chemical but it seems its more of a physical change..
    It's obvious bonds are broken. Im asking what the bonds are, is it colvalent, ionic or vander-walls.
    WHY Can't the BONDS just simply, go back together? The pencil still has it's properties, it's just seprated.

    Im in ap chemistry in highschool, your level of understanding is probably above mine, but my teacher couldnt answer this.
  19. May 15, 2006 #18
    I thought I already said that to put bonds back together requires an input of energy in this case.

    I appologize about misunderstanding you when you said physical change. By your definition, it is a physical change because you are not changing the chemical composition of the pencil graphite.
    Last edited: May 15, 2006
  20. May 15, 2006 #19
    Ok thanks, that answer's my question.

    Now could this be any type of energy?
  21. May 15, 2006 #20
    * Double post.
    Last edited: May 15, 2006
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