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Is gel liquid?

  1. May 13, 2005 #1
    Please help me in this. Are gel, cream and paste liquids? I'm getting the answer for primary school students. So, please help me explaining in simple way. Thank you!

  2. jcsd
  3. May 13, 2005 #2


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    I think they're all solids. cream might be a liquid.
  4. May 13, 2005 #3
    Look at the definition of liquid :)
  5. May 13, 2005 #4
    I think they are mixtures of both solids and liquids. For the most part the things you mentioned will evaporate or dry up when exposed to the air and leave behind some solids.
  6. May 13, 2005 #5


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    A solid is a state of matter, characterized by a definite volume and a definite shape (it resists deformation). Within a solid, atoms/molecules are relatively close together, or "rigid"; however, this does not prevent the solid from becoming deformed or compressed. In the solid phase of matter, atoms have a fixed spatial ordering; because all matter has some kinetic energy, the atoms in even the most rigid solid move slightly, but this movement is "invisible".

    A liquid is a phase of matter and a fluid whose volume is fixed under conditions of constant temperature and pressure, and, whose shape is usually determined by the container it fills. Furthermore, liquids exert pressure on the sides of a container as well as on anything within the liquid itself; this pressure is transmitted undiminished in all directions.

    Gel is a liquid, cream (like milk) is a liquid, cream (like ointment) is a liquid, paste is a liquid. For those who say othersise, pour or squeeze them into a small cup, and see if they spread out and form into the shape of their container.
  7. May 14, 2005 #6


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    Try semisolid !

    The boundary between a solid and a liquid is not well defined (whether in terms of viscosity or the ability to support shear stress), and things living in the grey area can safely be called semisolids.

    Mk, your definitions of a liquid lack any mention of time scales. A piece of glass, given sufficient time, will flow to fill a container and exert pressure on the side walls. But while some will call glass a liquid, most still like to think of it as a solid.
  8. May 14, 2005 #7


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    Solid, liquid and gas are the three major distinctions of the state of matter. However there are some materials which may exhibit charateristics of two states, such as gels, creams or pastes.

    As Gokul mentioned, "semi-solid" may be appropriate, but also perhaps semi-liquid. Glass is effectively an amorphous solid, i.e. not crystalline lattice structure. Glass actually flows (creeps) but very slowly. Concrete/cement also flow, which has interesting implications for many man-made structures, which should last a long-time.

    Gel's are a form of 'colloid'. From Wikipedia:
    Here are some definitions of colloid.

    from http://en.wikipedia.org/wiki/Colloid

    Schlumberger (oil services company) - http://www.glossary.oilfield.slb.com/Display.cfm?Term=colloid

    The is a good book, but hard to find - "Seven States of Matter" by Milton Gottlieb (1966). I read it about 30+ years ago, and it gives a good overview of the states of matter.
  9. May 14, 2005 #8
    are you sure??? because old glass was made larger at the bottom anyway, well, according to a historian atleast...

    what are these states???
  10. May 14, 2005 #9


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    How about aerogel?

    Gas? solid?
  11. May 14, 2005 #10
    can you breathe in this areogel? and if so, would you just fall to the bottom or float???
  12. May 14, 2005 #11
    Freshly mixed concrete appears to be a liquid, but it is made up of stone aggregate, cement, sand, and water. It's a mixture at this point of solids and liquid. If you remove a stone from this concrete you will find it to be very much a solid not liquid. In grade school science I remember discussing adding substances together and determining whether they were mixtures or new substances created through a chemical reaction. I think you can only apply the term solid, liquid, or gas to individual groups of the same molecules. Sure you can have 2 liquids in the same glass but its still a mixture.

    Lets say we have a glass filled with marbles and water, what would you consider this a solid or liquid....it's a mixture.
  13. May 14, 2005 #12


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    Aerogel, is much more solid than your typical gooey gel. It shears and it doesn't flow. Also importantly, it is anisotropic over microscopic scales.
  14. May 14, 2005 #13


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    This distinction is important for many kinds of gels where you will find that, on setting for long periods, the different components tend to partially separate. But even when invoking the rebuttal based on mixtures, there is sometimes a grey area. The counter-argument often used is that a state can be assigned to a homogeneous mixture but not a heterogeneous one. The grey area : where the crossover happens...
  15. May 14, 2005 #14
    This is a myth that was effectively debunked a couple years ago. The myth was started by someone examining a stained glass window in an old Cathedral in Europe. All the pieces of glass seemed to be thicker at the bottom than the top. The person concluded the glass had flowed over several centuries.

    As hexhunter was trying to point out, further examinations of Cathedral stained glass have shown that many windows from the same period have a statistically proper number of pieces that are thicker at the top than the bottom.

    All the glass back then was hand blown, and they had no way to regulate the thickness. It is likely that the maker of the window that precipitated this rumor just put all the glass in thick end down for consistancy's sake. They can't find any others like it.
  16. May 14, 2005 #15
    Here's a good article on the subject of glass.
  17. May 14, 2005 #16
    Yeah, that's good. Also a good discussion of the larger solid/liquid dichotomy.
  18. May 14, 2005 #17

    Ok I had to look up hetrogeneous :confused: anyway the description for hetrogeneous mixture gave granite as an example. For homogeneous air is used as an exapmle. Both in this case can be assigned a "state". Still if you seperate the components (in either mixture) which aren't bound chemically you get individual compounds with individual properties and states. By assigining states to mixtures we are just being incomplete in the description.
  19. May 14, 2005 #18


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    Hmmm...didn't know this. Interesting !!

    But in any case, the existence of creep at STP is well-known and well documented among several solids, including metals like indium.
  20. May 14, 2005 #19


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    Let me rephrase. A heterogeneous mixture need not necessarily have a state assigned to it.

    But virtually anything you have in reality is a mixture. Show me a pure, isolated element or compound and I'll show you an egg balancing on its tip. By not allowing a 'stat'e to be assigned to a mixture, you are grossly hampering the usefulness it provides to communication.
  21. May 14, 2005 #20
    Yeah. I used to love telling people that glass was a liquid.
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