Expansion of ice.

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#1 HydrogenBond

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Posted 17 September 2006 - 08:46 AM

Water and the formation of ice creates a unique situation in nature. Unlike almost all liquid to solid transitions, water expands when it forms ice. All other natural materials, with the exception of the metal antimony, do just the opposite. The superfiscial reason this occurs is that the crystal structure of ice leaves more intermolecular space than occurs in liquid water.

If one looks at this closely, a paradox appears to occur. The expansion of the ice crystal, increases the average distances of all the hydrogen bonds. If the hydrogen bonding is an electro-static attraction between positively charged hydrogen and the negative charged oxygen, the expansion of ice should be endothermic instead of exothermic, since the average distance between the charge dipoles is increasing throughout the ice.

The question becomes, where is the exothermic affect coming from which can not only compensate for the endothermic expansion of all the charge dipoles, but results in a highly exothermic phase change?

#2 Mercedes Benzene

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Posted 17 September 2006 - 08:58 AM

If one looks at this closely, a paradox appears to occur. The expansion of the ice crystal, increases the average distances of all the hydrogen bonds. If the hydrogen bonding is an electro-static attraction between positively charged hydrogen and the negative charged oxygen, the expansion of ice should be endothermic instead of exothermic, since the average distance between the charge dipoles is increasing throughout the ice.

The question becomes, where is the exothermic affect coming from which can not only compensate for the endothermic expansion of all the charge dipoles, but results in a highly exothermic phase change?

It doesn't matter that water expands when it freezes.
ALL freezing is an exothermic process... regardless of how the substance behaves in its new state.
That's what freezing is. A loss of energy to the environment.

#3 HydrogenBond

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Posted 17 September 2006 - 09:42 AM

Freezing is a liquid-solid phase change into a more stable state. The amount of energy given off by water from 2C to 1C is far less than from 1C to 0C. This large jump in exothermic output implies a very significant increase in stability, which releases a lot of energy. With the dipoles expanding endothermically, what is the source of the exothermic?

If we do an energy balance, the expansion of ice causes both the positive charge of hydrogen and the negative charges on oxygen to separate increasing the EM force potential in the hydrogen bonds. The increased positive charge of hydrogen does not offer any stability for hydrogen. The increased negative charge of oxygen increases the electron density around the oxygen. The result is that the extra negative charge stabilizes the oxygen through the octet rule and enhanced magnetic addition. This is the source of the exothermic output of expanding/freezing ice. The oxygen is pulling the electrons away from the hydrogne bonds, making hydrogen share at a further distance increasing proton potential in the process.

The expansion of ice stabilizes the oxygen, in doing so imparts enhanced positive charge onto the hydrogen. In another forum topic, electric ice, this positive charge becomes evident between rubbing ice particles in thunder clouds. The result is lightning.

#4 eric l

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Posted 17 September 2006 - 10:14 AM

The "weird" behaviour of water is indeed due to hydrogen bonds (not meant personally). It is not just the expansion of ice, but also the extremely high boiling point when compared to the chemical "neigbours" like NH3 (ammonia), HF or H2S which are all gasses at room temperature, or the very high surface tension (and a number of other things).
The best explanation for this is that "liquid" water is present as a plolymer (due to hydrogen bonds) rather than as a simple molecule. This also explains why water can easily get undercooled (cooled below 0°C without freezing up)
Freezing is a crystalization proces and requires similar molecules, rather than molecular chains of different length. In the same way, it is easy to crystalize pure dextrose, but with mixtures of dextrose, maltose and other oligosacharides you obtain a glassy structure rather than a crystaline one.
For boiling, you have again this transformation from polymeric liquid water to monomeric gaseous water, which acounts for the high value of the heath of evaporation.

#5 HydrogenBond

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Posted 17 September 2006 - 12:11 PM

If one looks at NH3, HCL, one does not get an expansion upon freezing. One may attribute this to the unequal hydrogen and unbonded orbitals preventing extended polymer structures. But if one looks at H2S, it too does not expand upon freezing. In the case of H2S, the secondary bonding is not technically hydrogen bonding but forms via purely electro-static bonds. Purely electro-static bonding does not allow expansion upon freezing. The partial covalent nature of hydrogen bonding adds something that can override the electrostatic attraction.

#6 eric l

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Posted 17 September 2006 - 12:37 PM

I do not think that hydrogen bonds play an important role in ammonia, hydrogen fluoride or hydrogen sulfide.
In water the oxygen atom has a spare pair of electrons, on which a proton (free H+ion) or hydrogen atom from an other molecule can fix itself upon. This gives a H3O+ion, with the H-atoms almost iun the same plane with the oxygen, or a (H2O)2 type polymer.
With HF or HCl you have an asymetricity in the molecule due to size difference, (and hence polarity) but not an inviting "free" pair of electrons ready to accept a proton or a hydrogen atom.
With NH3 you have of course the possibility of forming NH4+, but not in equilibrium with NH2- (only in aqueous solution, and then in equilibrium with OH-). I remember having read an explanation for that some years ago, but can not trace back where.
In the case of H2S the size of the sulphur atom is too large (compared to the oxygen atom in water) to have the same effect, the H3S+ structure is less probable than the H3O+structure.
In fact, strong hydrogen bonds are almost exclusively a water thing - they do occur to a lesser degree in methanol. The hydrogen bonds in the other cases are simply not strong enough to create clusters or polymers like they do with water.

#7 HydrogenBond

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Posted 20 September 2006 - 07:32 AM

Hydrogen bonds form when hydrogen is covalently bonded to highly electronegative atoms like N, O, Cl and F. Both ammonia and hydrogen floride form hydrogen bonds. With respect to liquid water forming polymers, this phenomena is connected, in part, to water having two pairs of active ends. (two hydrogen protons and two available electron orbitals). This allows every water molecule to hydrogen bond to two others thereby making extended structure possible.

What is strange about water polymers and ice is that water polymers is almost analogous to ice. As the temperature falls toward 0C, this slows down the water allowing the polymers to grow. At 0C, all the hydrogen move away from the oxygen (expansion) as oxygen pulls the shared hydrogen bonded electron density in, due to the partial covalent nature of hydrogen bonding and the higher electronegativity of oxygen.

Something that appears to parallel the exapnsion of the ice is connected to DNA. For the most part, DNA exists as a right hand double helix. It can also exist as a left handed helix, although this is far less common. One main difference between the two orientations is that the left handed helix is more compact and the more common right handed helix is fluffier. This suggests that the right handed DNA is the ice state of the DNA and the left handed helix is the water state of the DNA.

By these two terms I mean that the more expanded state of righthand DNA is implicit of oxygen and nitrogen pulling electron density in to make the hydrogen more electro-positive. This is an important aspect of the DNA that helps define the signiture potential of DNA. This is amplified by the extra hydrogen proton in every base pair.

#8 Michaelangelica

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Posted 21 September 2006 - 07:39 AM

I don't understand much of what you are saying but the question is a fascinating one. Water is so amazing.

What happens to highly compressed "Blue" ice such at that found in Antarctica and in some Icebergs? Has it been compacted?
Has it therefore not expanded but eventually (after a few miles of ice press down on it) contracted? How does this effect the hydrogen bond?

The severe damage to the Titanic was said to be due to the incredible hardness and compactness of the iceberg that hit it.

(What is 'fuzzy' DNA?)

#9 HydrogenBond

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Posted 26 September 2006 - 05:14 PM

The point I was trying to make ,with the expansion of ice, is that the accepted understanding of hydrogen bonding needs an ungrade to version 1.1.

Most know about the partial covalent nature of hydrogen bonds but tend to think of hydrogen bonds in terms of dipole potentials. The expansion of ice, is an interesting observation that creates an amomaly if only dipole forces are at work. The observed expansion logically implies an exothermic situation where opposite charges are separating. If only dipole interaction where at work, this could be used for perpetual motion since lowering the distance between charges will also be exothermic.

Since this is not possible, something more is happening, which in the case of the formation of ice, clearly dominates the assumed dipole nature of hydrogen bonding. This something else is connected to the high electronegativity of oxygen. Although the oxygen becomes negative to create a dipole and separates a dipole, this still gives off energy because it create a very stable atomic configuration.

This anomaly tells us about the true nature of hydrogen bonding. The high electronegativity of oxygen and nitrogen, to name two, keeps the hydrogen in a constant state of potential no matter if a hydrogen bond forms or not. Hydrogen bonds can lower this potential, but reaches a limit with respect to absolute hydrogen proton potential.

This is very important because it is the basis for life. The hydrogen bonding hydrogen are always at some level of potential This gives the extra umph that is philosophically called the life force. Philosophy saw this but could not put it into words. Science ignorred philosophy and have left out the most important variable of the living state.

DNA is assumed the most important, but even DNA is subject to the laws of hydrogen bonding, just like RNA, proteins, water and almost everything else in the cell. The perpetual hydrogen potential is what gives life to all these molecules, while also allowing them to integrate.

A good way to visualize the affect of proton potential and life, it is like a fuel that constantly attempts to burn and is able to give off some of its energy potential, but it is constantly restored back to potential due to strong electronegative interactions. Because this burn/restore always leads back to net potential, the protons organize themselves in ways that allows the most net burn. This organization results in cells. The cell did not result from random, but is due to the little ole hydrogen protons trying to lower their perpetual potential.

#10 Vending

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Posted 27 September 2006 - 10:11 AM

Most know about the partial covalent nature of hydrogen bonds but tend to think of hydrogen bonds in terms of dipole potentials.

I don't think so. I think chemistry represents a hydrogen bond as a resonance between the ionic and covalent bonds. I don't think that the covalent nature is ever forgot about -- as it is crutial to the behavoir of water. This is, of course, the exact same treatment that can be applied to every "bond" formation. Theoretically, there is really no formal distinction between a covalent and ionic bond (within the resonance formalism at least). That is, the construction of the bond (leading to energy stabilization) is the same in the ionic and covalent cases. Generally, the bond between species A and B can be expressed as the resonance between the structures A B, A+B-, and A-B -- the last being where the electrons lie between the two atoms. Rather, the difference between the ionic and covalent lies in which resonance structure is dominant -- the covalent or the ionic.

Although the oxygen becomes negative to create a dipole and separates a dipole, this still gives off energy because it create a very stable atomic configuration.

The question is answered by realizing that the covalent nature of the hydrogen bond is suffeciently strong that the most stable structure of water is not one where the molecules are in van der waals contact. Rather, as is the case with covalent bonding, the most stable spacing is one where the molecules (or atoms) are farther away than the sum of their respective radii.

Thus, we see why water expands as it freezes. In the liquid form, the molecules are in van der waals contact -- as they must be if they are a liquid. However, as water freezes, the molecules slow down and they no longer have the kenetic energy needed to overcome the extra binding eneregy that is gained by moving the molecules apart. Consequently, the water molecules are able to adopt their most stable structure -- one in which they are slightly farther apart (owing to the somewhat strong covalent nature of the hydrogen bond). Thus, ice is formed, and is less dense than water.

You see, it is the unusually strong covalent component of the h-bond that gives rise to the expansion of water. There is no need to revise the theory or to invoke some sort of "life force." Although i will readily admit that I did not fully follow that part of your post.

Perhaps you can expain more clearly what you mean? In particular, I found your discussion of potentials to be confusing and I was unsure as to wether or not you were invoking energetic or electronic potentials.

Anyway, i think it remains that the expasion of ice can be understood in the context of currently accepted thoery. At least in my mind

#11 HydrogenBond

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Posted 30 September 2006 - 07:09 AM

When looking at water one has to go back to the beginning and look at one water molecule. The dipoles form because of the covalent bonds between oxygen and hydrogen and because of the higher electronegativity of oxygen. Inspite of the dipole forming, this is the most stable state of a water molecule.

The partial negative charge on oxygen stabilizes the oxygen. In other words, there is no pressing need for oxygen to share this partial charge, since it took it from hydrogen because it offers extra octet stability. The hydrogen proton is a different story. It lost electron density to oxygen to become slightly positive. This positive charge is not stabilizing for the hydrogen but gives hydrogen a potential to share electron density. The result is the need to form hydrogen bonds.

Here is the situation with hydrogen bonding between two water molecules, the hydrogen has potential while the oxygen is stable. Oxygen and hydrogen just so happen to have opposite charges but the negative charge on oxygen does not count as much as the positive charge, since the negative charge stabilizes the oxygen. What the partial covalent nature of hydrogen bonding does is prevent the hydrogen from taking too much electron density away from oxygen, inspite of the charge attraction. The covalent bond is a better form of delocalized sharing compared to dipole interaction. This allows oxygen to get back some of the electron density hydrogen tries to share. If oxygen allowed hydrogen to share too much, it would become potentiated.

The net affect, is that hydrogen is always under potential. To lower its potential it needs to destabilize oxygen and pass the burden of potential. But oxygen is too electronegative and will form a covalent addendum to the dipole, which allows it to minimize its induced potential.

Exsiting theory correctly forms water and can see the dipole that results. From there it then looks at this ground state as being potentiated due to the dipole. It fails to realize the negative end of the dipole is actually very stable and has no need to share. The way to understand this is connected to the law of physics that says that the electromagnetic force is one force and not two separate forces. The magnetic addition within the orbitals of oxygen stabilizes the extra negative charge. When ice expands the oxygen is pushing the hydrogen away using magnetic repulsion. The primary burden of potential remains with the hydrogen.

In the living state, it is not cooincidental that water is the main component and all the active bio-structures use hydrogen bonding. The hydrogen has this inherant burden of potential that is perpetuated by oxygen and nitrogen. The living state make use of this potential and is animated and organized because of it.

#12 Vending

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Posted 03 October 2006 - 09:19 AM

When looking at water one has to go back to the beginning and look at one water molecule. The dipoles form because of the covalent bonds between oxygen and hydrogen and because of the higher electronegativity of oxygen. Inspite of the dipole forming, this is the most stable state of a water molecule.

Ok, i have very little to disagree with here, so lets just say that I agree with you so far for the sake of this discussion.

The partial negative charge on oxygen stabilizes the oxygen. In other words, there is no pressing need for oxygen to share this partial charge, since it took it from hydrogen because it offers extra octet stability.

OK, so now I have questions.
First, I will agree that the partial charge stbilizes the oxygen, but not for the reason you state. The oxygen is stabilized by the partial negative charge because it is more electronegative than the hydrogen. That is it. It has very little, if nothing, to do with the octet. The oxygen already has an octet due to the electron sharing (ie. the covalent bond) with the hydrogens. It cannot have "more" of an octet. As far as it is concerned (from an electron counting viewpoint) it has eight electrons.

Given that oxygen has an octet, already, then what leads to the dipole formation? Electronegativities. The idea is that the oxygen holds onto the electrons it shares with hydorgen more tightly than hydrogen does. Thus, there is slightly more electron density on the oxygen than on the hydrogen. NOTICE: The oxygen has more electron density. This has nothing to do with electron count.

The point I am trying to make is this; once the bonding orbital is made, then the electrons in that orbital belong to both the oxygen and the hydrogen together, however, the difference in electronegativity can affect the density of the electronic wavefunction around both nuclie. (but the electron count for each maintians the same.)

The hydrogen proton is a different story. It lost electron density to oxygen to become slightly positive. This positive charge is not stabilizing for the hydrogen but gives hydrogen a potential to share electron density. The result is the need to form hydrogen bonds.

As above; the hydrogen is not a proton, but a hyrogen atom. One with a filled shell. That is, as far at electron counting goes it has 2 electrons (a filled S shell). It did lose electron density to the oxygen, but not electrons.

Also, why do you claim that the formation of a positive charge is destabilizing for the hydrogen? It occurs because there is a difference in electronegativity between the oxygen and the hyrodgen. I think you must consider the FULL environment of the hydrogen. In the environment in which the hydrogen is surrounded by oxygens, the hydrogen is MORE stable with a positive charge. We know this must be true, since it occurs spontaneously. Thus, we see that if hydrogen is surrounded by oxygens, it would be unstable for it to carry a neutral or negative partial charge.

What the partial covalent nature of hydrogen bonding does is prevent the hydrogen from taking too much electron density away from oxygen, inspite of the charge attraction. The covalent bond is a better form of delocalized sharing compared to dipole interaction. This allows oxygen to get back some of the electron density hydrogen tries to share. If oxygen allowed hydrogen to share too much, it would become potentiated.

Actually, the covalent nature of the interaction does just the opposite. Hydrogen bonds are mostly electrostatic in nature. If they were totally electrostatic, they would not exchange or share any electron density at all. However, since the hydrogen bond is to some degree covalent, then it allows sharing. Thus, the covalent contribution to the bond is the only thing that is allowing charge sharing and, therefore, far from limiting it, it maximizes it.

Exsiting theory correctly forms water and can see the dipole that results. From there it then looks at this ground state as being potentiated due to the dipole. It fails to realize the negative end of the dipole is actually very stable and has no need to share. The way to understand this is connected to the law of physics that says that the electromagnetic force is one force and not two separate forces. The magnetic addition within the orbitals of oxygen stabilizes the extra negative charge. When ice expands the oxygen is pushing the hydrogen away using magnetic repulsion. The primary burden of potential remains with the hydrogen.

To summarize my points and where they disagree with yours;
1) There is no reason why the negative end of the dipole is more stable than the positive end. You have offered not proof of this. Furthermore, your reasoning is flawed, since you do not treat both the oxygen and hydrogen as having a full outershell, which, due to the covlant bond, they both do.

2) The partial covalent nature of the hydrogen bond does not limit the electron sharing in such a bond, but, rather, allows for electron sharing to occur.

3) What do you mean by "the magnetic addition within the orbitals of the oxygen stabilizes the ectra negative charge"? Again, both hydrogen and oxygen have full shells in water. Furthermore, when attempting to discuss the magnetic properties of a atom in a molecule, one must look at the molecule as a whole. Water is dimagnetic as a whole due to the full pairing of electrons in its orbitals. This is due to the covalent bond formation and nothing else. Changes is electronic density do not affect the whether something is dimagnetic or paramagnetic, just the relative intensity of the magnetic feild lines. It is the electronic pairing -- dictated by the orbital structures -- that detrmines gross magnetic properties. As such, it is soley a bonding issue. But perhaps i missunderstand your point?

In the living state, it is not cooincidental that water is the main component and all the active bio-structures use hydrogen bonding. The hydrogen has this inherant burden of potential that is perpetuated by oxygen and nitrogen. The living state make use of this potential and is animated and organized because of it.

Rather than assuming that water is perfect for life, I think it is better to assume that life is perfect for water. That is; life found a way to use water, not water is nessesary for life. Just a different perspective, that is all.

#13 Paul H

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Posted 21 October 2006 - 12:32 AM

I've often thought of this as a local 'violation' of 'thermodynamics'.

You take enery *out* of a system, and it becomes "more* organized.

Water to ice, I mean.

Now... why am I wrong? In a local sense.

#14 ronthepon

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Posted 21 October 2006 - 12:36 AM

Now that is precisely the reason why freezing in general takes place below a particular temperature, not above it.

Gibb's free energy change equation (Second law revolves around this):

${\Delta}G = {\Delta}H - T{\Delta}S$

Basically, the energy taken out of the system goes into the surroundings, and at that low temperature, the disorder (Entropy) increase in the surroundings is greater than the Entropy (Disorder) decrease in the system.

Thus total entropy (Disorder) increases anwhow.

#15 Eclogite

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Posted 21 October 2006 - 07:35 AM

I've often thought of this as a local 'violation' of 'thermodynamics'.

You take enery *out* of a system, and it becomes "more* organized.

Water to ice, I mean.

Now... why am I wrong? In a local sense.

Surely your problem is that while thermodynamics may be examined in 'local' settings, the laws of thermodynamics do not have a local component. You must consider the entirety of the system, and that system may be closed. If you look at 'local' effects you are, potentially, looking at an open system, where the laws will not be applicable.

#16 HydrogenBond

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Posted 21 October 2006 - 01:13 PM

To summarize my points and where they disagree with yours;
1) There is no reason why the negative end of the dipole is more stable than the positive end. You have offered not proof of this. Furthermore, your reasoning is flawed, since you do not treat both the oxygen and hydrogen as having a full outershell, which, due to the covlant bond, they both do.

2) The partial covalent nature of the hydrogen bond does not limit the electron sharing in such a bond, but, rather, allows for electron sharing to occur.

3) What do you mean by "the magnetic addition within the orbitals of the oxygen stabilizes the ectra negative charge"? Again, both hydrogen and oxygen have full shells in water. Furthermore, when attempting to discuss the magnetic properties of a atom in a molecule, one must look at the molecule as a whole. Water is dimagnetic as a whole due to the full pairing of electrons in its orbitals. This is due to the covalent bond formation and nothing else. Changes is electronic density do not affect the whether something is dimagnetic or paramagnetic, just the relative intensity of the magnetic feild lines. It is the electronic pairing -- dictated by the orbital structures -- that detrmines gross magnetic properties. As such, it is soley a bonding issue. But perhaps i missunderstand your point?

One of the problem with looking at the covalent bonds of water is looking at them only in terms of the electron wave functions. One also needs to do an electron count and look at electron particles. The oxygen shares its octet with hydrogen. Oxygen does not have it own octet or it would be called oxide, which is very stable. The closer to oxide oxygen can get, the more stable the octet of oxygen. In other words, because of sharing with hydrogen, the oxygen actually only has 5-7 electrons time averaged in its octet, with the hydrogen having the rest.

The reason octet stability is so important is force addition. When two electrons are in an orbital, stability requires opposite spin. If one uses the right hand rule (current direction, magnetic field direct and resultant force direction) the opposite spin and circulation creates an attractive force between the orbital electrons. One can take two wires and run electricity through them, if the current goes in the opposite direction the wires will attract. With octet stability, the vector force addtions are between all eight electrons in 3-D. So if oxygen is able to get 7 instead of 6.8 (just to use numbers) that adds a little extra force addition that adds stability to the oxygen.

Although the chemical structure of the hydrogen connected to the oxygen of water shows hydrogen having two electrons (shares), it actually starts out with only two halves of an electron (time averaged) equal to one electron. Hydrogen only brought one electron into the bond with oxygen and with oxygen much more electronegative, hydrogen can not end up with more than one time averaged electron. In fact, it looses part of its one time average electron to have less than one time averaged electron. This makes the hydrogen net positive and therefore in potential. There is no stability to this. Even the two partially shared electrons are not giving a full orbital addtiive force around hydrogen, since there is less than one time averaged electron near hydrogen.

When hydrogen bonds form, the hydrogen attempts to get one full time averaged electron with maximum force addition. But to do this, it must take away some of the electron density that is stabilizing the almost oxygen octet through the force addtion. This is closed system with what hydrogen gains equal to what oxygen's loses. The partial covalent nature of hydrogen bonds, allows a shifting/sharing of electron density, allowing oxygen to regain some of its force stability, while passing the burden back to the hydrogen. Oxygen essentially, asserts its higher electronegativity even through hydrogen bonds to maximizes its movement toward octet stability.