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B Question about the states of matter

  1. May 11, 2016 #1
    I have a question, and it is this: why is it that your hand can go through a gas or liquid while the same can't be done with solids? Is it because of density?
     
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  3. May 11, 2016 #2

    ProfuselyQuarky

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    Indeed, it has to do with density. Do you know the difference between how atoms are arranged in the different states of matter?
     
  4. May 11, 2016 #3
    Kind of. I believe I do in a way.
     
  5. May 11, 2016 #4

    ProfuselyQuarky

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    See the image http://www.msm.cam.ac.uk/SeeK/slg.html [Broken]?

    The atoms are closely packed together in the solid, but they become increasingly spread apart for the liquid and gas. There is more space between the atoms in the two latter states.
     
    Last edited by a moderator: May 7, 2017
  6. May 11, 2016 #5
    Yeah, I actually did know that, but thanks, anyway.
     
    Last edited by a moderator: May 7, 2017
  7. May 11, 2016 #6

    ProfuselyQuarky

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    So if you knew that, what exactly were you asking? You could clarify and then I could help you better :smile:
     
  8. May 11, 2016 #7
    I just wasn't completely sure about it.
     
  9. May 11, 2016 #8

    ProfuselyQuarky

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    Okay, then. Now you're sure :)
     
  10. May 11, 2016 #9

    jbriggs444

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    The density of a substance has quite little to do with whether you can move your hand through it.

    You can push your hand through liquid water more easily than you can push your hand through a cube of expanded polystyrene (styrofoam). What matters is not so much how dense the material is, but how firmly the component molecules are bound into a matrix.
     
  11. May 11, 2016 #10
    You mean as in how tightly packed they are, right?
     
  12. May 11, 2016 #11

    jbriggs444

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    More like how inflexible the packing arrangement.
     
  13. May 13, 2016 #12
    It's not just density. Water is denser than ice, you know. In a solid, all the molecules are bound together in an orderly formation, so you have to break many bonds to move your hand through. In a liquid, the molecules stick together but aren't in a tight formation. The molecules are all disorganized. So, when you push your hand through, the molecules can bend shift around relatively freely.
     
  14. May 13, 2016 #13

    ProfuselyQuarky

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    In other words, the space between molecules can change.
     
  15. May 13, 2016 #14

    jbriggs444

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    No. The arrangement of the molecules can change. The [average] space between them need not change.
     
  16. May 13, 2016 #15

    ProfuselyQuarky

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    But it can. That's all I was saying.
     
  17. May 13, 2016 #16
    I don't know if the difference between a liquid and solid is totally cut and dry. There's not a whole lot of difference between a very high viscosity liquid and and amorphous solid. Practically speaking, solids won't flow, but ductile metals can be pressed into shape with enough force.
     
  18. May 13, 2016 #17

    ProfuselyQuarky

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    That is something I often wonder. Like, is lotion a solid or liquid? A semi-liquid? A semi-solid?
     
  19. May 13, 2016 #18

    jbriggs444

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    In a liquid, the average space between molecules does not change. And yet liquids flow. In a solid, the average space between molecules does not change. But solids do not flow [much]. The average spacing between molecules can not be the determining feature. That is what I am trying to point out.
     
  20. May 13, 2016 #19

    ProfuselyQuarky

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    Fair enough.

    Now what about this: is lotion a solid or liquid? A semi-liquid? A semi-solid?
     
  21. May 13, 2016 #20

    jbriggs444

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    A suspension of oil droplets in water. Or of water droplets in oil. Kashishi's point seems good. The distinction between a solid and a liquid is not always sharp, especially in composite substances.
     
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