| Topic: |
Science > Physics |
| User: |
"Maleki" |
| Date: |
09 Mar 2005 11:55:02 AM |
| Object: |
Specific heat of water |
Why is it so high? Where does the rendered energy go before
starting to raise water molecules' kinetic energy? And after
the spill over eventually starts to raise KE, what else
keeps absorbing additional energy, delaying further increase
in temperature? Strange stuff!
--
"doshmane dAnA bolandat mikonad
bar zaminat mizanad nAdAn dust"
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| User: "Uncle Al" |
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| Title: Re: Specific heat of water |
09 Mar 2005 01:28:30 PM |
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Maleki wrote:
Why is it so high? Where does the rendered energy go before
starting to raise water molecules' kinetic energy? And after
the spill over eventually starts to raise KE, what else
keeps absorbing additional energy, delaying further increase
in temperature? Strange stuff!
Several excellent proposals will be given. Look up the specific heat
of solid and molten lithium hydride and add one more.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
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| User: "tadchem" |
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| Title: Re: Specific heat of water |
09 Mar 2005 12:33:23 PM |
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Maleki wrote:
Why is it so high? Where does the rendered energy go before
starting to raise water molecules' kinetic energy?
It goes to breaking hydrogen bonds between separate water molecules.
Each water molecule can participate in as many as 4 intermolecular
bonds in which hydrogen ions are shared between two oxygens.
The hydrogen bonds turn water into something of a three-dimensional
polymer, which gives it the anomalously high melting and boiling points
(considering it has a lower molecular weight than neon - melting point
-248.6=B0 C, boiling point -246.06=B0 C).
And after
the spill over eventually starts to raise KE, what else
keeps absorbing additional energy, delaying further increase
in temperature? Strange stuff!
More hydrogen bonds. Until water boils, the molecules are pretty
thoroughly cross linked to one another.
Tom Davidson
Richmond, VA
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| User: "bz" |
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| Title: Re: Specific heat of water |
09 Mar 2005 01:45:38 PM |
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"tadchem" <thomas.davidson@dla.mil> wrote in news:1110393203.343219.58830
@f14g2000cwb.googlegroups.com:
It goes to breaking hydrogen bonds between separate water molecules.
Each water molecule can participate in as many as 4 intermolecular
bonds in which hydrogen ions are shared between two oxygens.
The hydrogen bonds turn water into something of a three-dimensional
polymer, which gives it the anomalously high melting and boiling points
(considering it has a lower molecular weight than neon - melting point
-248.6° C, boiling point -246.06° C).
H2S(bp -60c), which is similar to H2O, except for the substitution of
Sulfur for the oxygen has almost twice the weight water might be a better
comparison as it contains hydrogen and is not a 'noble gas'. It does NOT
have hydrogen bonding.
Also, F, O, and N can take part in hydrogen bonds.
[quote]
The increased interaction between molecules containing H-F, H-O or H-N
bonds is termed hydrogen bonding.
[unquote]
--
bz
please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.
bz+sp@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
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| User: "N:dlzc D:aol T:com \dlzc\ N: dlzc1 D:cox" |
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| Title: Re: Specific heat of water |
09 Mar 2005 12:48:48 PM |
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Dear tadchem:
"tadchem" <thomas.davidson@dla.mil> wrote in message
news:1110393203.343219.58830@f14g2000cwb.googlegroups.com...
Maleki wrote:
And after
the spill over eventually starts to raise
KE, what else keeps absorbing additional
energy, delaying further increase in
temperature? Strange stuff!
More hydrogen bonds. Until water boils, the
molecules are pretty thoroughly cross
linked to one another.
Is the dissociation in water (pH) driven by the (cosmic and
natural) radiation background in which we are immersed, or is
this a separate phenomenon? I know immersing a Co-60 souce in
water produces some hydrogen peroxide...
David A. Smith
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| User: "tadchem" |
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| Title: Re: Specific heat of water |
09 Mar 2005 01:12:28 PM |
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N:dlzc D:aol T:com (dlzc) wrote:
<snip>
Is the dissociation in water (pH) driven by the (cosmic and
natural) radiation background in which we are immersed, or is
this a separate phenomenon? I know immersing a Co-60 souce in
water produces some hydrogen peroxide...
The 'driving force' for dissociation of water into positive and
nevgative ions seems to be the presence of other positive and negative
ions - electrolyes. When *scrupulously* purified (as is done in
preparation for conductivity experiments), water is a non-conductor and
a damned good dielectric.
The presence of a positive or negative ion shifts the balance of
hydrogen ions on a double layer 'solvation sphere' (the collection of
water molecules that surround an ion in solution) resulting in the
dissociation of a very large number of water molecules:
http://bio.winona.msus.edu/berg/ILLUST/Na+H2O.gif
This is not a trivial topic (my dissertation discussed dipole solvation
of electrons in liquid ammonia), so let me know how much detail you
want.
The H2O2 produced in water by Co-60 could result from the reduction by
beta particles or by the direct reduction of water by an active metal.
I would have to look into that further. I know H2O2 is produced
commercailly by simple electrolysis.
Tom Davidson
Richmond, VA
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| User: "N:dlzc D:aol T:com \dlzc\ N: dlzc1 D:cox" |
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| Title: Re: Specific heat of water |
09 Mar 2005 01:32:51 PM |
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Dear tadchem:
"tadchem" <thomas.davidson@dla.mil> wrote in message
news:1110395548.875954.118020@f14g2000cwb.googlegroups.com...
N:dlzc D:aol T:com (dlzc) wrote:
<snip>
Is the dissociation in water (pH) driven by the (cosmic and
natural) radiation background in which we are immersed, or is
this a separate phenomenon? I know immersing a Co-60 souce in
water produces some hydrogen peroxide...
The 'driving force' for dissociation of water into positive and
nevgative ions seems to be the presence of other positive and
negative
ions - electrolyes. When *scrupulously* purified (as is done
in
preparation for conductivity experiments), water is a
non-conductor and
a damned good dielectric.
I have experience with 18 meg ohm water (which is less pure than
what you describe). But it still read "pH 7"... pH doesn't
describe the absolute *numbers* of ions, only the ratio between +
and -. We can drop this, since I can't take it much further.
The presence of a positive or negative ion shifts the balance
of
hydrogen ions on a double layer 'solvation sphere' (the
collection of
water molecules that surround an ion in solution) resulting in
the
dissociation of a very large number of water molecules:
http://bio.winona.msus.edu/berg/ILLUST/Na+H2O.gif
Thanks. Makes sense, as it provides a favorable "place" for
discontinuities to reside. Just what is the trigger for the
discontinuity.
This is not a trivial topic (my dissertation discussed dipole
solvation
of electrons in liquid ammonia), so let me know how much detail
you
want.
The cognates are enough. "solvation sphere" can go a ways (352
hits). You'd swamp me about your second paragraph... ;>)
The H2O2 produced in water by Co-60 could result from the
reduction by
beta particles or by the direct reduction of water by an active
metal.
I would have to look into that further. I know H2O2 is
produced
commercailly by simple electrolysis.
Agreed. I believe there is a path from an excited state where
OH* is unlikely, but not unable, to bond to an OH.
Acetone is pretty interesting stuff too... as far as hydrogen
bonds, melting point, and boiling point goes. (Just to plug into
"PD"s response to you.)
Thanks.
David A. Smith
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| User: "PD" |
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| Title: Re: Specific heat of water |
09 Mar 2005 01:53:33 PM |
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N:dlzc D:aol T:com (dlzc) wrote:
Dear tadchem:
"tadchem" <thomas.davidson@dla.mil> wrote in message
news:1110395548.875954.118020@f14g2000cwb.googlegroups.com...
N:dlzc D:aol T:com (dlzc) wrote:
<snip>
Is the dissociation in water (pH) driven by the (cosmic and
natural) radiation background in which we are immersed, or is
this a separate phenomenon? I know immersing a Co-60 souce in
water produces some hydrogen peroxide...
The 'driving force' for dissociation of water into positive and
nevgative ions seems to be the presence of other positive and
negative
ions - electrolyes. When *scrupulously* purified (as is done
in
preparation for conductivity experiments), water is a
non-conductor and
a damned good dielectric.
I have experience with 18 meg ohm water (which is less pure than
what you describe). But it still read "pH 7"... pH doesn't
describe the absolute *numbers* of ions, only the ratio between +
and -. We can drop this, since I can't take it much further.
I don't think this is right. It indicates that the concentration of H+
(or rather H3O+) is 1E-7 M, doesn't it?
And Tom's remark is interesting, because I'd never heard of a *reason*
for water's amphoteric self-ionization.
The presence of a positive or negative ion shifts the balance
of
hydrogen ions on a double layer 'solvation sphere' (the
collection of
water molecules that surround an ion in solution) resulting in
the
dissociation of a very large number of water molecules:
http://bio.winona.msus.edu/berg/ILLUST/Na+H2O.gif
Thanks. Makes sense, as it provides a favorable "place" for
discontinuities to reside. Just what is the trigger for the
discontinuity.
This is not a trivial topic (my dissertation discussed dipole
solvation
of electrons in liquid ammonia), so let me know how much detail
you
want.
The cognates are enough. "solvation sphere" can go a ways (352
hits). You'd swamp me about your second paragraph... ;>)
The H2O2 produced in water by Co-60 could result from the
reduction by
beta particles or by the direct reduction of water by an active
metal.
I would have to look into that further. I know H2O2 is
produced
commercailly by simple electrolysis.
Agreed. I believe there is a path from an excited state where
OH* is unlikely, but not unable, to bond to an OH.
Acetone is pretty interesting stuff too... as far as hydrogen
bonds, melting point, and boiling point goes. (Just to plug into
"PD"s response to you.)
Does acetone "ice" float on top?
Thanks.
David A. Smith
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| User: "N:dlzc D:aol T:com \dlzc\ N: dlzc1 D:cox" |
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| Title: Re: Specific heat of water |
09 Mar 2005 02:10:20 PM |
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Dear PD:
"PD" <pdraper@yahoo.com> wrote in message
news:1110398013.180012.47750@g14g2000cwa.googlegroups.com...
N:dlzc D:aol T:com (dlzc) wrote:
Dear tadchem:
"tadchem" <thomas.davidson@dla.mil> wrote in message
news:1110395548.875954.118020@f14g2000cwb.googlegroups.com...
N:dlzc D:aol T:com (dlzc) wrote:
<snip>
Is the dissociation in water (pH) driven by the
(cosmic and natural) radiation background in
which we are immersed, or is this a separate
phenomenon? I know immersing a Co-60
souce in water produces some hydrogen
peroxide...
The 'driving force' for dissociation of water into
positive and nevgative ions seems to be the
presence of other positive and negative ions
- electrolyes. When *scrupulously* purified
(as is done in preparation for conductivity
experiments), water is a non-conductor and
a damned good dielectric.
I have experience with 18 meg ohm water
(which is less pure than what you describe).
But it still read "pH 7"... pH doesn't describe
the absolute *numbers* of ions, only the ratio
between + and -. We can drop this, since I
can't take it much further.
I don't think this is right. It indicates that the
concentration of H+ (or rather H3O+) is
1E-7 M, doesn't it?
You are likely right. My instrument undoubtedly provided ions
into the mix that allowed "measurement".
And Tom's remark is interesting, because
I'd never heard of a *reason* for water's
amphoteric self-ionization.
....
Acetone is pretty interesting stuff too... as far as hydrogen
bonds, melting point, and boiling point goes. (Just to plug
into
"PD"s response to you.)
Does acetone "ice" float on top?
A quick perusal did not provide a density for solid acetone. I
don't know. But it does have a pretty wide solid-liquid and
liquid-gas temperature range, at 1 atm. I used to use it with
dry ice to limit/evaluate feedgas dewpoint to an ozone generator.
David A. Smith
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| User: "PD" |
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| Title: Re: Specific heat of water |
09 Mar 2005 02:23:46 PM |
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N:dlzc D:aol T:com (dlzc) wrote:
Dear PD:
"PD" <pdraper@yahoo.com> wrote in message
news:1110398013.180012.47750@g14g2000cwa.googlegroups.com...
N:dlzc D:aol T:com (dlzc) wrote:
Dear tadchem:
"tadchem" <thomas.davidson@dla.mil> wrote in message
news:1110395548.875954.118020@f14g2000cwb.googlegroups.com...
N:dlzc D:aol T:com (dlzc) wrote:
<snip>
Is the dissociation in water (pH) driven by the
(cosmic and natural) radiation background in
which we are immersed, or is this a separate
phenomenon? I know immersing a Co-60
souce in water produces some hydrogen
peroxide...
The 'driving force' for dissociation of water into
positive and nevgative ions seems to be the
presence of other positive and negative ions
- electrolyes. When *scrupulously* purified
(as is done in preparation for conductivity
experiments), water is a non-conductor and
a damned good dielectric.
I have experience with 18 meg ohm water
(which is less pure than what you describe).
But it still read "pH 7"... pH doesn't describe
the absolute *numbers* of ions, only the ratio
between + and -. We can drop this, since I
can't take it much further.
I don't think this is right. It indicates that the
concentration of H+ (or rather H3O+) is
1E-7 M, doesn't it?
You are likely right. My instrument undoubtedly provided ions
into the mix that allowed "measurement".
It has always been my understanding that ion "seeds", or contamination
of any kind, is not needed. K_w, the ion dissociation constant of
water, is 1E-14, period. That's why Tom's remark surprised me. I, for
one, would be delighted to have this idea amended.
PD
And Tom's remark is interesting, because
I'd never heard of a *reason* for water's
amphoteric self-ionization.
...
Acetone is pretty interesting stuff too... as far as hydrogen
bonds, melting point, and boiling point goes. (Just to plug
into
"PD"s response to you.)
Does acetone "ice" float on top?
A quick perusal did not provide a density for solid acetone. I
don't know. But it does have a pretty wide solid-liquid and
liquid-gas temperature range, at 1 atm. I used to use it with
dry ice to limit/evaluate feedgas dewpoint to an ozone generator.
David A. Smith
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| User: "tadchem" |
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| Title: Re: Specific heat of water |
09 Mar 2005 02:24:33 PM |
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N:dlzc D:aol T:com (dlzc) wrote:
Dear tadchem:
I have experience with 18 meg ohm water (which is less pure than
what you describe). But it still read "pH 7"... pH doesn't
describe the absolute *numbers* of ions, only the ratio between +
and -.
Close, but not quite right...
In water at room temperature for the dissociation reaction
H2O <-> H+ + OH-
the equilibrium constant K (the product of the concentrations of
hydrogen ions - formally [H+] - and hydroxyl ions - formally [OH-]) is
K = [H+]*[OH-] = 10^-14 (about, there is some slight temperature
dependence).
When the H+ and OH- come *only* from dissociation of water, the
concentration are equal and about 10^-7 moles per liter.
When there is some solute that (one way or another) provides either H+
or OH- ions, then the equilibrium involved in the dissociation reduces
the concentration of the other ion accordingly.
For example, if you added 1 mole of sodium hydroxide (soda ash, NaOH) -
about 40 grams - to a liter of water, you would have a concentration of
OH- of 1 mole per liter, and a concentration of H+ of 10^-14 moles per
liter.
The pH is defined to be -1 times the common logarithm of the
concentration of the hydrogen ions, so the solution described above
would have a pH of 14.
Similarly, 1 mole (only 35.45 grams) of hydrogen chloride in a liter of
eater would give you a solution with a pH of 0 - a little stronger than
stomach acid. Cut that by a factor of 10 and you raise the pH by 1.0
units, only 0.001 moles of HCl in a liter will give you a pH of 3.0 -
about the same as stomach acid.
In an indirect way, pH describes the *concentration* of H+ and, by
inference using the equilibrium constant expression for the
dissociation, the concentration of OH- as well; the product of the two
is a _constant_.
Thanks. Makes sense, as it provides a favorable "place" for
discontinuities to reside. Just what is the trigger for the
discontinuity.
The ions are *very* small (~0.1 nm) and provide a fairly strong
electrostatic field which polarizes the water molecules.
Agreed. I believe there is a path from an excited state where
OH* is unlikely, but not unable, to bond to an OH.
That is more likely in the gas phase, as OH* (with a neutral charge) is
very unstable in water.
Acetone is pretty interesting stuff too... as far as hydrogen
bonds, melting point, and boiling point goes. (Just to plug into
"PD"s response to you.)
Liquid ammonia is almost as polar a solvent as water, but without the
dissociation.
Tom Davidson
Richmond, VA
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| User: "Maleki" |
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| Title: Re: Specific heat of water |
09 Mar 2005 01:15:47 PM |
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On 9 Mar 2005 10:33:23 -0800, tadchem wrote:
It goes to breaking hydrogen bonds between separate water molecules.
Each water molecule can participate in as many as 4 intermolecular
bonds in which hydrogen ions are shared between two oxygens.
The hydrogen bonds turn water into something of a three-dimensional
polymer, which gives it the anomalously high melting and boiling points
(considering it has a lower molecular weight than neon - melting point
-248.6° C, boiling point -246.06° C).
Then why is it still liquid. Wouldn't that make it solid or
jellylike?
And if that's the reason, then specific heat of water is
sharply different for its gas form?
--
"khodAyA:
roshde elmi va aghliye marA az fazilate _ta'assob_
va _ehsAs_ va _eshrAgh_ mahrum nasAz."
- Ali Shari'ati
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| User: "PD" |
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| Title: Re: Specific heat of water |
09 Mar 2005 12:58:36 PM |
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tadchem wrote:
Maleki wrote:
Why is it so high? Where does the rendered energy go before
starting to raise water molecules' kinetic energy?
It goes to breaking hydrogen bonds between separate water molecules.
Each water molecule can participate in as many as 4 intermolecular
bonds in which hydrogen ions are shared between two oxygens.
The hydrogen bonds turn water into something of a three-dimensional
polymer, which gives it the anomalously high melting and boiling
points
(considering it has a lower molecular weight than neon - melting
point
-248.6=B0 C, boiling point -246.06=B0 C).
And after
the spill over eventually starts to raise KE, what else
keeps absorbing additional energy, delaying further increase
in temperature? Strange stuff!
More hydrogen bonds. Until water boils, the molecules are pretty
thoroughly cross linked to one another.
Tom Davidson
Richmond, VA
I'm glad a chemist is answering this question. Water is truly a marvel
and its properties are singularly responsible for the presence of life
on the planet (aside from any agent that might have put it together
that way on purpose, mind you). Anomalously large high melting and
boiling points, anomolously large heat capacities, unusual density
behavior around the melting point, etc.
However, water isn't the only compound that enjoys strong
intermolecular hydrogen bonding. Is it true that other compounds that
exhibit hydrogen bonding also exhibit these unusual properties?
PD
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