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Why paper contracts when burnt?

  1. Dec 12, 2015 #1
    I have observed many times, that when a newspaper is burnt, its writings become smaller.

    Do the paper really contract when burnt?
     
  2. jcsd
  3. Dec 12, 2015 #2

    SteamKing

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    It's not clear what you are describing.

    When I burn a newspaper, it turns to ash.
     
  4. Dec 12, 2015 #3
    Hello Ajayraho,
    I think your observation has credence.
    The paper would have to get smaller and smaller as it burns.

    For one thing all the water in the paper is driven off by the heat. The percentage change in volume night not be all that much, depending upon the makeup of the paper.
    Next the carbon compounds are turned into gases that can burn with the oxygen in the air. So the paper itself is actually losing mass.

    If you don't disturb the ash remaining, you can still sometimes read the now smaller print, at least where it hasn't curled up on itself.
     
  5. Dec 13, 2015 #4
    the paper itself actually loosing massmoreove moreover there were water before in the paper and vaporized after burnt the peper. However paper are not pure elements so the VDW between partical actually maintain constant but number of partical decrease so the paper contracts.
     
  6. Dec 13, 2015 #5

    A very satisfying answer..
    So whats the reason behind the yellowing of papers, when kept for a long period of time???
     
  7. Dec 16, 2015 #6
    Hi Ajayraho
    actually, paper are not white from the origanls. it is yellow, we use some chemical bleacher to bleach the paper, however, the chemical will left ln the paper and during a long time, the chemical on the paper will reacts with paper which give a yellow colour on the paper
     
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