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Glass is not a liquid?

  1. May 28, 2013 #1
    Since my high school days, I learned that glass is a liquid. (Science naive students thought glass is solid, and the smarty pants knew it was actually a liquid:) Yesterday, while I was telling this interesting fact to my daughter, my wife argued that glass is solid. I googled to explain them why glass is a liquid, but apparently science web sites points out that "glass is liquid" is an urban legend. Seems like I was wrong all these years. I thought of posting this here because some people here might be thinking glass is a liquid.
  2. jcsd
  3. May 28, 2013 #2
    How you define "liquid" is the important question to ask. Depending on your definition, it can be either a liquid or solid.

    If you had a 100 year old glass pane, and you measured the top and bottom, you'd find that the bottom would be slightly thicker.
  4. May 28, 2013 #3
    Idk, jobyts. Looks like the jokes on you...:redface:
  5. May 28, 2013 #4
  6. May 28, 2013 #5


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    liquids take the shape of their container. Glass doesn't.
  7. May 28, 2013 #6
    Is water liquid at zero gravity?
  8. May 28, 2013 #7
    It might be a myth, I've never tried it myself :tongue:, but it claims on the bottom exactly what I mentioned in my first post.

  9. May 28, 2013 #8
    Are you serious? Tell me you haven't seen the NASA videos with the guys sucking liquid water/juice balls out of mid-air on the space station, etc.. Those are liquids, it's just the surface tension that makes them look like balls. As Physics_UG pointed out, you can see the balls morph as if they would take the shape of their container.
  10. May 28, 2013 #9
    We had a long, long thread about this a few years back. For all intents and purposes, glass is a solid. It won't flow over the course of a few hundred years. However, by some strict technical definition, according to former mentor, Gokul90210, it is often classified as a liquid. You might see some flow over billions of years.
  11. May 28, 2013 #10
    Can you please point me to a video? Searching with the keywords (guys sucking liquid water/juice balls) you mentioned points me to weird videos :)

    Unless there is an external force (gravity or something else) to overcome the surface tension, any matter would retain its shape. In this case, before the sucking action by the astronauts , was the water ball liquid or solid? Given enough force, most (if not all) solids could become liquids.

    As mentioned before (by Astrum), the definition of liquid/solid is a loose one, and assumes normal forces acting upon them. (as earth's surface gravity). A definition for liquids as it takes-the-shape-of-container is not complete. With that definition, a freely falling rain drop (with no other external forces on it) is not a liquid.
  12. May 28, 2013 #11
    How about this one?

  13. May 28, 2013 #12
    Thanks Dirac :)
  14. May 28, 2013 #13
    Or this one:

  15. May 28, 2013 #14


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    This is related:


    It is a matter of viscosity. Very high viscosity makes us think about tar as of a solid, yet given enough time it flows. I am not sure if the glass will flow at the room temperature - at least not in typical timescales, at least not all glass types - but the same reasoning applies.

    Basically we are trying to apply separate names to a continuous reality that doesn't care about our definitions.
  16. May 28, 2013 #15


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    It depends on its temperature, just like when it is on earth.
  17. May 28, 2013 #16


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    It's an amorphous solid. Generally it retains it's shape. Under pressure/stress, glass and ceramics (e.g., concrete) will deform/creep very slowly.
  18. May 28, 2013 #17

    Andy Resnick

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    Materials that are commonly referred to as 'glass' are disordered solids. Glassy materials include colloids, foams, emulsions, granular materials, and are characterized by dramatic changes to macroscopic properties (viscosity) without corresponding changes to microscopic properties (structure) as the 'glass transition' is approached.

    The nature of the glass transition is not completely understood.
  19. May 28, 2013 #18


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    Er, that question implies you are talking about water floating in a ball in the middle of the space station, not in a container. But how do you think it got there!
  20. May 28, 2013 #19


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    To add to this, I live close to Strawbery Banke (not a typo), where some of the oldest original windows in the country are still in use. The process that made glass windows in the 1600s left one side thicker than the other (unintentionally), window installers would simply place the thicker side on the bottom for stability. The taper itself, however, was not intentional just a byproduct of the spinning that was done to make the pane as smooth as possible. The best windows were considered to be the ones that had the least taper to them and were, therefore, more distortion free.
  21. May 28, 2013 #20
    Glass is neither solid nor liquid. It's all an illuminati plot.
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