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Sodium acetate trihydrate - initiation of crystallization.

  1. Apr 2, 2007 #1
    Hi,

    I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
    small metal disk which is stressed and will produce a click if squeezed
    correctly. Once clicked the liquid will crystallize and the heat of fusion
    provides the hand warming. I've been asked by my children how it works. As
    they are inquisitive children, one answer leads to another question. I've
    now come to the point where I cannot supply the answer and neither, it
    appears, can Google. The question is this - how does the shock wave from the
    click of the metal disk initiate the crystallization? I assume the
    Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
    unavailable, otherwise it would be prone to spontaneous crystallization.
    Does the shock wave force a few molecules into the correct alignment
    somehow? Any answers would help preseve my credibility.
    TIA.

    Steve.
     
  2. jcsd
  3. Apr 2, 2007 #2
    On 1 abr, 17:28, Russel Sprout <s...@idontthinkso.net> wrote:
    > Hi,
    >
    > I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
    > small metal disk which is stressed and will produce a click if squeezed
    > correctly. Once clicked the liquid will crystallize and the heat of fusion
    > provides the hand warming. I've been asked by my children how it works. As
    > they are inquisitive children, one answer leads to another question. I've
    > now come to the point where I cannot supply the answer and neither, it
    > appears, can Google. The question is this - how does the shock wave from the
    > click of the metal disk initiate the crystallization? I assume the
    > Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
    > unavailable, otherwise it would be prone to spontaneous crystallization.
    > Does the shock wave force a few molecules into the correct alignment
    > somehow? Any answers would help preseve my credibility.
    > TIA.
    >
    > Steve.


    Shock waves can be quite powerful. Certainly even a finger click is
    sufficient to induce chemical changes and nucleation. There are a
    number of phenomena linked to this. There is luminescence in bubbles.
    This was investigated extensively in a television program. When a
    bubble collapses the gas can reach a high temperature. Not high enough
    for thermonuclear reactions to be sure, but high enough to glow.

    The Physics is basically this. Let us take a whip which is tapered
    towards one end. A modest jolt will send a wave down it. Because of
    tapering this wave gets amplified and the crack heard is sonic boom.
    Bubbles do exactly the same thing. your finger generates enormous
    force for a short instant of time. This leads to a shock wave which is
    powerful enough to initiate nucleation. A few microseconds will
    suffice.


    - Ian Parker
     
  4. Apr 4, 2007 #3
    Russel Sprout wrote:
    >
    > Hi,
    >
    > I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
    > small metal disk which is stressed and will produce a click if squeezed
    > correctly. Once clicked the liquid will crystallize and the heat of fusion
    > provides the hand warming. I've been asked by my children how it works. As
    > they are inquisitive children, one answer leads to another question. I've
    > now come to the point where I cannot supply the answer and neither, it
    > appears, can Google. The question is this - how does the shock wave from the
    > click of the metal disk initiate the crystallization? I assume the
    > Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
    > unavailable, otherwise it would be prone to spontaneous crystallization.
    > Does the shock wave force a few molecules into the correct alignment
    > somehow? Any answers would help preseve my credibility.
    > TIA.


    Stuff like, "Clicking the disk forces a few molecules to change to a
    solid state, and the rest of the liquid then rushes to solidify as
    well."

    They don't know either. Does the gizmo have an appended patent
    number?

    http://www.uspto.gov/patft/index.html

    <http://www.sfu.ca/physics/ugrad/courses/teaching_resources/demoindex/thermal/th4c/patentheatpack.html>
    technical ramblings

    http://www.hot-pad.com/products.php

    DO NOT microwave these things.

    --
    Uncle Al
    http://www.mazepath.com/uncleal/
    (Toxic URL! Unsafe for children and most mammals)
    http://www.mazepath.com/uncleal/lajos.htm#a2
     
  5. Apr 4, 2007 #4
    Russel Sprout <s@idontthinkso.net> wrote:
    >Hi,
    >
    > I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
    >small metal disk which is stressed and will produce a click if squeezed
    >correctly. Once clicked the liquid will crystallize and the heat of fusion
    >provides the hand warming. I've been asked by my children how it works. As
    >they are inquisitive children, one answer leads to another question. I've
    >now come to the point where I cannot supply the answer and neither, it
    >appears, can Google. The question is this - how does the shock wave from the
    >click of the metal disk initiate the crystallization? I assume the
    >Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
    >unavailable, otherwise it would be prone to spontaneous crystallization.
    >Does the shock wave force a few molecules into the correct alignment
    >somehow? Any answers would help preseve my credibility.
    >TIA.
    >
    >Steve.


    My quick search revealed a quickie explanation at:

    http://en.wikipedia.org/wiki/Sodium_acetate#_note-0 ,
    or
    http://tinyurl.com/2harqz ,

    with a reference to another interesting page at:

    www.atmos.washington.edu/2003Q3/101/demonstrations/fake_latentheat_supersaturation.html
    or
    http://tinyurl.com/2ddcxs

    This site refers to more pages:

    www.howstuffworks.com/question290.htm

    and a demo at

    http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA3/MAIN/ACETATE/PAGE1.HTM
    or
    http://tinyurl.com/2b88x7

    According to the above references, you are on the right track. Your
    credibility hasn't been tarnished.
     
  6. Apr 4, 2007 #5
    On 1 abr, 17:28, Russel Sprout <s...@idontthinkso.net> wrote:
    > Hi,
    >
    > I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
    > small metal disk which is stressed and will produce a click if squeezed
    > correctly. Once clicked the liquid will crystallize and the heat of fusion
    > provides the hand warming. I've been asked by my children how it works. As
    > they are inquisitive children, one answer leads to another question. I've
    > now come to the point where I cannot supply the answer and neither, it
    > appears, can Google. The question is this - how does the shock wave from the
    > click of the metal disk initiate the crystallization? I assume the
    > Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
    > unavailable, otherwise it would be prone to spontaneous crystallization.
    > Does the shock wave force a few molecules into the correct alignment
    > somehow? Any answers would help preseve my credibility.
    > TIA.
    >
    > Steve.


    There is just one thing further you can tell your kids. Supernovae and
    star formation. The shock wave of a supernova triggers star formation.
    The Sun was formed shortly after a supernova explosion. We know this
    because the oldest meterorites have tracks associated with Pu(244)
    half life 80 million years in them. This is quite an astonishing
    result. Plutonium does indeed form in rocks.

    BTW - Centrifuges to me show lack of faith! An Islamic country should
    look for a Plutonium mine!

    - Ian Parker
     
  7. Apr 4, 2007 #6
    Uncle Al wrote:
    > Russel Sprout wrote:
    >> Hi,
    >>
    >> I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
    >> small metal disk which is stressed and will produce a click if squeezed
    >> correctly. Once clicked the liquid will crystallize and the heat of fusion
    >> provides the hand warming. I've been asked by my children how it works. As
    >> they are inquisitive children, one answer leads to another question. I've
    >> now come to the point where I cannot supply the answer and neither, it
    >> appears, can Google. The question is this - how does the shock wave from the
    >> click of the metal disk initiate the crystallization? I assume the
    >> Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
    >> unavailable, otherwise it would be prone to spontaneous crystallization.
    >> Does the shock wave force a few molecules into the correct alignment
    >> somehow? Any answers would help preseve my credibility.
    >> TIA.

    >
    > Stuff like, "Clicking the disk forces a few molecules to change to a
    > solid state, and the rest of the liquid then rushes to solidify as
    > well."
    >
    > They don't know either. Does the gizmo have an appended patent
    > number?
    >
    > http://www.uspto.gov/patft/index.html
    >
    > <http://www.sfu.ca/physics/ugrad/courses/teaching_resources/demoindex/thermal/th4c/patentheatpack.html>
    > technical ramblings
    >
    > http://www.hot-pad.com/products.php
    >
    > DO NOT microwave these things.


    Which is, of course, engineering speak for "stick it in the uwave and
    see what happens". I assume some scientist here can supply the theory as
    to why it *might* be a bad idea. Or at least, an interesting one.
    Something to do with superheated liquids etc?

    --
    Dirk

    http://www.onetribe.me.uk - The UK's only occult talk show
    Presented by Dirk Bruere and Marc Power on ResonanceFM 104.4
    http://www.resonancefm.com
     
  8. Apr 5, 2007 #7
    Dirk Bruere at NeoPax wrote:
    >
    > Uncle Al wrote:
    > > Russel Sprout wrote:
    > >> Hi,
    > >>
    > >> I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
    > >> small metal disk which is stressed and will produce a click if squeezed
    > >> correctly. Once clicked the liquid will crystallize and the heat of fusion
    > >> provides the hand warming. I've been asked by my children how it works. As
    > >> they are inquisitive children, one answer leads to another question. I've
    > >> now come to the point where I cannot supply the answer and neither, it
    > >> appears, can Google. The question is this - how does the shock wave from the
    > >> click of the metal disk initiate the crystallization? I assume the
    > >> Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
    > >> unavailable, otherwise it would be prone to spontaneous crystallization.
    > >> Does the shock wave force a few molecules into the correct alignment
    > >> somehow? Any answers would help preseve my credibility.
    > >> TIA.

    > >
    > > Stuff like, "Clicking the disk forces a few molecules to change to a
    > > solid state, and the rest of the liquid then rushes to solidify as
    > > well."
    > >
    > > They don't know either. Does the gizmo have an appended patent
    > > number?
    > >
    > > http://www.uspto.gov/patft/index.html
    > >
    > > <http://www.sfu.ca/physics/ugrad/courses/teaching_resources/demoindex/thermal/th4c/patentheatpack.html>
    > > technical ramblings
    > >
    > > http://www.hot-pad.com/products.php
    > >
    > > DO NOT microwave these things.

    >
    > Which is, of course, engineering speak for "stick it in the uwave and
    > see what happens". I assume some scientist here can supply the theory as
    > to why it *might* be a bad idea. Or at least, an interesting one.
    > Something to do with superheated liquids etc?



    The clicker is a small metal disk. On does NOT microwave extended
    metal objects. Put a CD in your micrwoave and give it 3 seconds.

    --
    Uncle Al
    http://www.mazepath.com/uncleal/
    (Toxic URL! Unsafe for children and most mammals)
    http://www.mazepath.com/uncleal/lajos.htm#a2
     
  9. Apr 5, 2007 #8

    chemisttree

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Actually you can microwave metal objects in the microwave oven without much fuss. Metal foils are a different story!

    Remember, the interior of the microwave oven is entirely made of metal. Try it for yourself and see. Microwave a cup of coffee with a metal spoon. Nothing happens except the spoon gets a little warmer than the coffee. Metal foils will have some photoelectric effects and sparking can occur.

    The clicker in the handwarmer will get pretty hot but so will the supersaturated solution of sodium acetate. The salt solution is almost as effective a microwave absorber as is metal!

    In supersaturated solutions, the chemical potential of the solution is much higher than it is at equilibrium. The clicker produces pressure waves that send the chemical potential soaring at the interface of the clicker and the sodium acetate solution. This overpotential at the surface of the clicker is all that is needed to force the supersaturated solution to crystallize.
     
  10. Apr 6, 2007 #9
    Uncle Al wrote:
    > Dirk Bruere at NeoPax wrote:
    >> Uncle Al wrote:
    >>> Russel Sprout wrote:
    >>>> Hi,
    >>>>
    >>>> I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
    >>>> small metal disk which is stressed and will produce a click if squeezed
    >>>> correctly. Once clicked the liquid will crystallize and the heat of fusion
    >>>> provides the hand warming. I've been asked by my children how it works. As
    >>>> they are inquisitive children, one answer leads to another question. I've
    >>>> now come to the point where I cannot supply the answer and neither, it
    >>>> appears, can Google. The question is this - how does the shock wave from the
    >>>> click of the metal disk initiate the crystallization? I assume the
    >>>> Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
    >>>> unavailable, otherwise it would be prone to spontaneous crystallization.
    >>>> Does the shock wave force a few molecules into the correct alignment
    >>>> somehow? Any answers would help preseve my credibility.
    >>>> TIA.
    >>> Stuff like, "Clicking the disk forces a few molecules to change to a
    >>> solid state, and the rest of the liquid then rushes to solidify as
    >>> well."
    >>>
    >>> They don't know either. Does the gizmo have an appended patent
    >>> number?
    >>>
    >>> http://www.uspto.gov/patft/index.html
    >>>
    >>> <http://www.sfu.ca/physics/ugrad/courses/teaching_resources/demoindex/thermal/th4c/patentheatpack.html>
    >>> technical ramblings
    >>>
    >>> http://www.hot-pad.com/products.php
    >>>
    >>> DO NOT microwave these things.

    >> Which is, of course, engineering speak for "stick it in the uwave and
    >> see what happens". I assume some scientist here can supply the theory as
    >> to why it *might* be a bad idea. Or at least, an interesting one.
    >> Something to do with superheated liquids etc?

    >
    >
    > The clicker is a small metal disk. On does NOT microwave extended
    > metal objects. Put a CD in your micrwoave and give it 3 seconds.


    Ah... thought you were referring to supersatured Na acetate rather than
    a piece of metal. Although I have to say that I found the CD in the
    microwave to be quite impressive.

    Ditto eggs. And to keep on topic, does anyone have any idea of the
    internal pressure needed to rupture an egg?

    --
    Dirk

    http://www.onetribe.me.uk - The UK's only occult talk show
    Presented by Dirk Bruere and Marc Power on ResonanceFM 104.4
    http://www.resonancefm.com
     
  11. Apr 9, 2007 #10
    "Russel Sprout" <s@idontthinkso.net> wrote in message
    news:57a0moF2berukU1@mid.individual.net...
    > Hi,
    >
    > I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
    > small metal disk which is stressed and will produce a click if squeezed
    > correctly. Once clicked the liquid will crystallize and the heat of fusion
    > provides the hand warming. I've been asked by my children how it works. As
    > they are inquisitive children, one answer leads to another question. I've
    > now come to the point where I cannot supply the answer and neither, it
    > appears, can Google. The question is this - how does the shock wave from
    > the
    > click of the metal disk initiate the crystallization? I assume the
    > Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
    > unavailable, otherwise it would be prone to spontaneous crystallization.
    > Does the shock wave force a few molecules into the correct alignment
    > somehow? Any answers would help preseve my credibility.
    > TIA.
    >

    Thanks all,

    So that's it, the shock wave aligns a few molecules in close enough
    proximity to start the process of crystallization, probably. Somehow, I'd
    been hoping for something a little more exotic. The irony is, that the pack
    was going to be used during a fairly high altitude outing (my wife gets cold
    hands easily), as it turned out it was calm and sunny and on the S facing
    scree slope, a cooling pack would have ben a better idea.

    Thanks again,
    Steve.
     
  12. Apr 10, 2007 #11
    Russel Sprout wrote:
    >
    > "Russel Sprout" <s@idontthinkso.net> wrote in message
    > news:57a0moF2berukU1@mid.individual.net...
    > > Hi,
    > >
    > > I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
    > > small metal disk which is stressed and will produce a click if squeezed
    > > correctly. Once clicked the liquid will crystallize and the heat of fusion
    > > provides the hand warming. I've been asked by my children how it works. As
    > > they are inquisitive children, one answer leads to another question. I've
    > > now come to the point where I cannot supply the answer and neither, it
    > > appears, can Google. The question is this - how does the shock wave from
    > > the
    > > click of the metal disk initiate the crystallization? I assume the
    > > Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
    > > unavailable, otherwise it would be prone to spontaneous crystallization.
    > > Does the shock wave force a few molecules into the correct alignment
    > > somehow? Any answers would help preseve my credibility.
    > > TIA.
    > >

    > Thanks all,
    >
    > So that's it, the shock wave aligns a few molecules in close enough
    > proximity to start the process of crystallization, probably. Somehow, I'd
    > been hoping for something a little more exotic. The irony is, that the pack
    > was going to be used during a fairly high altitude outing (my wife gets cold
    > hands easily), as it turned out it was calm and sunny and on the S facing
    > scree slope, a cooling pack would have ben a better idea.


    They are available - two-chambered plastic pouches, water and either
    ammonium nitrate or urea. Mix and you have a cold pack. It doesn't
    reverse for reuse.

    Hot bandages are iron filings, activated charcoal, salt, water, and
    sawdust sealed in an oxygen barrier bag. When you breach containment
    the iron oxidizes over a few hours and the reaction provides sustained
    warmth. The same chemistry is used in oxygen-scrubbing sachets, in
    the manner of silica gel desiccant packs for water, for air-sensitve
    bottles of pharamceuticals and the like. We all know about oily rags
    (especially linseed oil in a wood or print shop) reacting with air,
    warming, and igniting.

    If you were Al Gore green you would have sheets of solar cells on your
    back and hat to sustainable-resource non-polluting solar power your
    reusable electrical warmers (presumably not fabricated in countries
    overflowing with objects of tolerence). You would then learn why
    engineers respect thermodynamics when designing capital equipment
    installations. Only the math is consequential.

    --
    Uncle Al
    http://www.mazepath.com/uncleal/
    (Toxic URL! Unsafe for children and most mammals)
    http://www.mazepath.com/uncleal/lajos.htm#a2
     
  13. Apr 10, 2007 #12
    Russel Sprout wrote:
    >
    > "Russel Sprout" <s@idontthinkso.net> wrote in message
    > news:57a0moF2berukU1@mid.individual.net...
    > > Hi,
    > >
    > > I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
    > > small metal disk which is stressed and will produce a click if squeezed
    > > correctly. Once clicked the liquid will crystallize and the heat of fusion
    > > provides the hand warming. I've been asked by my children how it works. As
    > > they are inquisitive children, one answer leads to another question. I've
    > > now come to the point where I cannot supply the answer and neither, it
    > > appears, can Google. The question is this - how does the shock wave from
    > > the
    > > click of the metal disk initiate the crystallization? I assume the
    > > Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
    > > unavailable, otherwise it would be prone to spontaneous crystallization.
    > > Does the shock wave force a few molecules into the correct alignment
    > > somehow? Any answers would help preseve my credibility.
    > > TIA.
    > >

    > Thanks all,
    >
    > So that's it, the shock wave aligns a few molecules in close enough
    > proximity to start the process of crystallization, probably. Somehow, I'd
    > been hoping for something a little more exotic. The irony is, that the pack
    > was going to be used during a fairly high altitude outing (my wife gets cold
    > hands easily), as it turned out it was calm and sunny and on the S facing
    > scree slope, a cooling pack would have ben a better idea.


    They are available - two-chambered plastic pouches, water and either
    ammonium nitrate or urea. Mix and you have a cold pack. It doesn't
    reverse for reuse.

    Hot bandages are iron filings, activated charcoal, salt, water, and
    sawdust sealed in an oxygen barrier bag. When you breach containment
    the iron oxidizes over a few hours and the reaction provides sustained
    warmth. The same chemistry is used in oxygen-scrubbing sachets, in
    the manner of silica gel desiccant packs for water, for air-sensitve
    bottles of pharamceuticals and the like. We all know about oily rags
    (especially linseed oil in a wood or print shop) reacting with air,
    warming, and igniting.

    If you were Al Gore green you would have sheets of solar cells on your
    back and hat to sustainable-resource non-polluting solar power your
    reusable electrical warmers (presumably not fabricated in countries
    overflowing with objects of tolerence). You would then learn why
    engineers respect thermodynamics when designing capital equipment
    installations. Only the math is consequential.

    --
    Uncle Al
    http://www.mazepath.com/uncleal/
    (Toxic URL! Unsafe for children and most mammals)
    http://www.mazepath.com/uncleal/lajos.htm#a2
     
  14. May 24, 2007 #13
    So that's it, the shock wave aligns a few molecules in close enough
    proximity to start the process of crystallization, probably. Somehow, I'd
    been hoping for something a little more exotic. The irony is, that the pack
    was going to be used during a fairly high altitude outing (my wife gets cold
    hands easily), as it turned out it was calm and sunny and on the S facing
    scree slope, a cooling pack would have ben a better idea.


    Um, is it really a shock wave effect or just generation of nucleation sites to catalyse crystallisation.

    I had though that it was like getting a supercooled bottle of beer etc, where minimal movement can cause (sadly) complete crystallisation.

    I dont know if the metal disc would harbour any salt crystals in surface imperfections or perhaps metal fragments act as nuclei??
     
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