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Stupid Question?

  1. Feb 7, 2004 #1
    Ok, is there any solid, liquid, or gas that becomes heavier as it gets warmer and lighter as it gets colder? Like a reverse lava lamp.

    The little physics I know says no but I Know VERY little, you know?

    CJ
     
  2. jcsd
  3. Feb 7, 2004 #2
    ice, below 4 degrees celsius, i think does this
     
  4. Feb 7, 2004 #3

    LURCH

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    If making a "reverse lava lamp" is the primary goal, perhaps a reversed approach is more appropreiate. There are many fluid mediums that thicken when cooled and thin out when heated. An object of near-neutral buoyancee would float in the thicker medium, and sink as it thinned.

    Just a thought.
     
  5. Feb 7, 2004 #4
    answers' answers so far

    Hadn't thought of ice Lethe. But I would like something that doesn't change it's physical properties so radically with the change. Does mercury fit the bill? if so is there something similar?

    Alas no Lurch the reverse lava lamp was just the analogy. But tell me more of this liquid.
    [?]

    CJ
     
  6. Feb 9, 2004 #5
    I dont see how any could increase or decrease of mass.

    2 grams of H20 is 2 grams, liquid, solid or vapor.

    Nautica
     
  7. Feb 9, 2004 #6

    chroot

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    Re: Re: Stupid Question?

    lethe,

    I think all ice is below 4 degrees Celsius. :wink: I assume you just mean water.

    nautica,

    I think he's using "light" and "heavy" to refer to density.

    - Warren
     
  8. Feb 10, 2004 #7
    There are minerals like zirconium tungstate that have a negative coefficient of thermal expansion, but I don't know of any blobby stuff, offhand, that would do this. Surely there class of polymers somewhere that do this.
     
  9. Feb 12, 2004 #8

    Tom Mattson

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    Re: Re: Re: Stupid Question?

    Two words: Ha Ha

    Really?? I assumed he just meant negative 4oC.
     
  10. Feb 19, 2004 #9
    Water reaches it's maximum density at 4° C, expands, due to thermicity, in either direction, from that point.
     
  11. Feb 25, 2004 #10
    ICE

    ice is only lighter because it traps air, but pure ice is the same wensity as liquid h20


    nothing fits this discription as losing density as it cools.
     
  12. Feb 25, 2004 #11

    FZ+

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    Whaa...? As far as I am aware, ice is less dense than liquid water (within certain limits) because the alignment of hydrogen bonds within the solid creates a more stable crystal lattice where the solid is less dense.

    eg. http://www.pa.msu.edu/~sciencet/ask_st/040694.html
     
  13. Mar 5, 2004 #12
    Well, I'm certainly no expert, but I recall that purified ice(such as used in commercial ice blocks for sculptures) are very dense, and greatly depend on reducing air entrapement. Interesting. The next time we use a commercial ice block, I will save a piece and see if it floats in standard water.
     
  14. Mar 6, 2004 #13
    FZ+ posted what is, to the best of my knowledge, the right responce, 'trapped air' simply adds to ice's floatation, but even without any air at all, it will still float in water...("normal ice"...means STP and 'tapwater')

    EDIT Ooops not STP as that is well above the freezing point, water reaches Max density at 4 C it expands, in either thermal direction, from there.

    Water does not change 'mass' when expanding, or contracting, it changes density (mass to volume)
     
    Last edited: Mar 7, 2004
  15. Mar 6, 2004 #14

    EL

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    Agree! The answer to lehte´s question is no! (As long as we are in the NR-limit)...
     
  16. Apr 14, 2004 #15
    pure ice is still less dense than pure water. and higher temperature does mean higher mass if you take energy into account. (extremely unmeasurable)
     
  17. May 19, 2004 #16

    Ice could adopt different phases that are more dense than water depending on the pressure and temperature, but most of these could not be taken out of that environment and plunked into liquid water at room temp and pressure.

    Here is a very nice explanation:
    http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA2/MAIN/ICECUBE/CD2R1.HTM

    Don't forget to check the link about deuterated water!! I never thought about it but there it is before your very ice.



    l
     
  18. May 21, 2004 #17

    Gokul43201

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    The answer to your question is contained in posts by Chroot and Parsons. Water is what you need. Cool it below 4 deg C and it becomes lighter. Heat it up to 4 and it becomes heavier.

    The reason for this is (perhaps) the formation of meta-stable hydrogen bonds - which are more stable in ice - that try to induce a non-close packing.
     
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