Hot water freezes faster than cold water

[alexander]

oh, i forget, all the cool effects you can get out of water and corn starch:

 

YouTube - Amazing Liquid http://www.youtube.com/watch?v=nq3ZjY0Uf-g&feature=related

 

i'll describe some other cool ones when i'm back, after lunch :confused:

[HydrogenBond]

Although water is very common, it is argumentatively the most complicated substance. Water has 63 anomalies that have been investigated, including hot water freezing faster than cold.

 

Water anomalies

[TheBigDog]

I am a long way from HS chemistry, but I remember hypothesizing about the behavior of water versus other molecular structures, and always thought that the "bent" shape of a water molecule had to be significant, versus the linear shape of something like CO2.

 

Bill

[HydrogenBond]

In chemistry water is normally represented as a bent molecule with an almost tetrahedral shape with two hydrogen atoms and two non bonded electron pairs.

 

What they have found is the two non bonded electrons pairs sort of merge between where they thought the two non bonded electrons were, much closer to the oxygen atom.

 

 

When water forms ice then the tetrahedral sort of returns. But when water is hydrogen bonded to some proteins, the water is triangular. The bent shape allows the hydrogen to share the electrons on another water.

[koji8123]

Evaporation is important but you have left out a big part of the puzzle. Heating water drives out all the dissolved gasses. Dissolved gasses act like antifreeze driving the freezing point down making it harder to freeze water that contains the gasses. Heated water not only cools fast it also freezes closer to the freezing point of pure water.

 

right that's why if you were to boil the water, evaporating most of the minerals in the water to get it closer to H20.

[alexander]

right that's why if you were to boil the water, evaporating most of the minerals in the water to get it closer to H20.

 

:)

 

methinks it works the other way around, since mineral's melting and evaporation points are much, much higher then that of water, it is water that evaporates, and minerals remain (hence why they make distilled water by collecting and condensing the vapor)

 

simple experiment, really, take some water, and add salt to it, mix it till there is no more salt, now set the pot down on a burner, and boil the water out, what are you left with, in the pot?

[Dutchdivco]

My 1st post, after intro'ing myself. Water is a fascinating stuff, no doubt.Read its the only substance that expands, when heated or cooled. (Not counting things like milk, which is largely water).Anyone know of an explanation or theory as to why it expands when frozen? Jim

[Moontanman]

My 1st post, after intro'ing myself. Water is a fascinating stuff, no doubt.Read its the only substance that expands, when heated or cooled. (Not counting things like milk, which is largely water).Anyone know of an explanation or theory as to why it expands when frozen? Jim

 

Actually Jim, other substances do indeed expand when frozen, gallium, bismuth, acetic acid, antimony and silicon come to mind. This process has to do with the atoms in the crystal lattice in some substances being packed further apart than the liquid.

[Dutchdivco]

Ahh, but do they also expand when heated. Not argueing here, far from it.Just going by a stray comment on another forum, that SAID that H2o is the only substance that expands when heated or cooled.Wondered why. Another stray thought; Read up on the origin of DMSO, the source for MSM.Said it comes from algae, that grows in coastline wetlands. When the water evaporates, it carries the DMSO with it, into clouds, and down with rain. Absorbed into the soil, then into plants, eaten by animals, both of which we eat. This is why its so ubiquitous.My point is those who talk about using rainwater, and then distilling it, to get a 'pure' water to experiment with.DMSO would be in the rainwater, even after distilling, although admittedly in small quantities.And DMSO has some REALLY strange qualities! Wonder if some of the anamolies of water are because of the DMSO in it? I don't know if its even possible/practical to remove the DMSO.Anyway, just thinking,...Jim

[Moontanman]

Ahh, but do they also expand when heated. Not argueing here, far from it.Just going by a stray comment on another forum, that SAID that H2o is the only substance that expands when heated or cooled.Wondered why. Another stray thought; Read up on the origin of DMSO, the source for MSM.Said it comes from algae, that grows in coastline wetlands. When the water evaporates, it carries the DMSO with it, into clouds, and down with rain. Absorbed into the soil, then into plants, eaten by animals, both of which we eat. This is why its so ubiquitous.My point is those who talk about using rainwater, and then distilling it, to get a 'pure' water to experiment with.DMSO would be in the rainwater, even after distilling, although admittedly in small quantities.And DMSO has some REALLY strange qualities! Wonder if some of the anamolies of water are because of the DMSO in it? I don't know if its even possible/practical to remove the DMSO.Anyway, just thinking,...Jim

 

Yes they expand when heated, water contracts until it at a certain point (cold) and then begins to expand as it freezes so do these other substances. Once above this densest point water and these substances expand as well (hot) What is DMSO?

 

Moderation Note: Responses dealing with DMSO have been moved to 11485

[Kharakov]

In chemistry water is normally represented as a bent molecule with an almost tetrahedral shape with two hydrogen atoms and two non bonded electron pairs.

....

What they have found is the two non bonded electrons pairs sort of merge between where they thought the two non bonded electrons were, much closer to the oxygen atom.

....

When water forms ice then the tetrahedral sort of returns. But when water is hydrogen bonded to some proteins, the water is triangular. The bent shape allows the hydrogen to share the electrons on another water.

 

Side note for you (Bond, H-bond): 2 different groups (one definitely published in the Journal of Magnetic Resonance, the other I am not sure of at this point) are working on room temperature solid state water in various materials (it started with concrete).

 

One has approached this from the experimental angle, observing tetrahedral jumps with NMR, another has approached it from the theoretical angle calculating that tetrahedral jumps occur using mathematical physics simulations. Not all that sure who/what the other group is, I just know that someone approached it from the theoretical angle (I might be able to dig around and find who it is...).

 

k

[Essay]

Journal of Magnetic Resonance,

k

Deuterium NMR relaxation experiments, low temperature deuterium NMR lineshape analysis, and FTIR spectra are consistent with a new model for solid state jump dynamics of water in 2H2O-synthesized kanemite and 2H2O-hydrated Na+-Zeolite A. Exchange occurs between two populations of water: one in which water molecules are directly coordinated to sodium ions and experience C2 symmetry jumps of their OH bonds, and a population of interstitial water molecules outside the sodium ion coordination sphere that experience tetrahedral jumps of their OH bonds. For both samples the C2 jump rate is much faster than the tetrahedral jump rate. 2H NMR relaxation experiments match well with the fast exchange regime of the model over a wide range of temperatures, including room temperature and above.

For hydrated Zeolite A, the kinetic activation parameters (dH, dS) for the tetrahedral and C2 symmetry jumps are: dHtet = +17 kJ/mol, dStet = −109 J/(mol K), and dHc2= +19 kJ/mol, dSc2= −20 J/(mol K). For kanemite, dHtet = +23 kJ/mol, dStet = −69 J/(mol K), and dHc2= +23 kJ/mol, dSc2= −11 J/(mol K).

 

...C2 jumps???

"C2 jumps" NMR

 

A multinuclear nuclear magnetic resonance study of t-butylthiol

SANDRMAO OIBROEKAN' D RODERICKE. WASYL~SHEN

Depczrtnlerlt of Chernistry, Dc~lhortsie University, Hnlgczx, N.S., Ccznnda B3H 453

Received February 12, 1985

A multinuclear nuclear magnetic resonance study of t-butylthiol

or

http://article.pubs.nrc-cnrc.gc.ca/ppv/RPViewDoc?issn=1480-3291&volume=63&issue=11&startPage=2926

 

In the rapid motion limit, the effect of jumps between sites of three-fold or greater symmetry is exactly the same as for rotational diffusion. Once this limit is reached, one cannot distinguish, for example, between 120" jumps or continuous rotation about a C3 axis. On the other hand, rapid jumps and diffusion about a C2 axis yield substantially different spectra (7-9, 11, 12). Theory predicts that 180" flips about a C2 axis in t-butyl compounds will result in an effective asymmetry parameter of 1....

The situation for more complex motion - e.g. a combination of C2 jumps and Cx jumps about different axes - is much more complex, and will not be dealt with here.

...

Since neither rapid diffusion or fast C3 jumps predict [asymmetry], the highly asymmetric lineshapes observed in this phase imply that C2 jumps must be involved in the reorientation of the molecule.

Further discontinuous changes in the deuterium nmr line-shapes do not take place until 164 K (d.o. compound) or 166 K (SD isotopomer), corresponding to the solid 111 --> solid 11 phase transition. At 164 K, the ...spectrum... undergoes further narrowing to a featureless peak of - 1 kHz in width with low intensity shoulders.

===

 

Ack! What an interesting way to waste a couple of hours.

 

So the C2 orientation is the one between the tetrahedral (C3) orientation (through the center of the face rather than thru the corners of the cube).

The one which HBond notes predominates in some bonding situations.

Thanks HB, ...interesting as always.... :)

===

 

Kharakov, that was a fascinating link on the Zeolite/kanemite hydration studies.

Thanks mucho:

 

It's neat that they include the Entropy, dS (delta S), in their measurements of the kinetic activation energies for these different conformations of "orbitals." ...the tetrahedral is more stable by a few Joules (compare with the kiloJoules for the OH bonds).

===

 

Whatever the precise details are, IMHO it's obvious that the changing shape of water molecules in various conditions (including phase changes) affects its packing behaviour--and thus its volume.

 

...as to the hot water freezing faster "topic" I don't know, but the dissolved gases theory sounds plausible....

This would be a good Science Fair Project for some kids!

 

 

~ :)

[logy]

My 1st post, after intro'ing myself. Water is a fascinating stuff, no doubt.Read its the only substance that expands, when heated or cooled. (Not counting things like milk, which is largely water).Anyone know of an explanation or theory as to why it expands when frozen? Jim

 

umm the explanation is fairly streight forward:

generally liquids expand when heated and shrink when cooled because when they are hotter, the mulecules move faster and need 'room to move'.

 

water has an intersting charcteristic due to it's molecular V shape and strong H bonds, so that when it is frozen is takes more space for each molecule. i found a web page with a nice diargam that demonstrates that

 

at the top you have ice and at the bottom you have water. in water the V shaped molecules are closer to each other because the hydrogen atoms (small balls) are not bonded to oxygen (large balls) from another molecule, while in ice every hydrogen is bonded to an oxygen from another molecule (represented by the rods that are connecting the balls), creating that larger tertahedral shape.

[HydrogenBond]

If you took NaCl and cooled it to freezing the liquid to solid transition will get denser as the atoms align into the crystal lattice since this is the most efficient packing and is at lower energy. Water aligns into a tetrahedral state as it changes phase to solid. The main difference is the partial covalent nature of hydrogen bonds. For the atomic orbitals to align properly the covalent aspect of the bonding needs to spread out to get the wave functions at minimum energy.

 

Even in liquid water, at any given temperature, high density water zones are at higher energy than low density water. This seems counter intuitive but is explained because low density water has better tetrahedral structuring. But it needs to spread out to make this work. This indicates that although H-bonds are both ionic and covalent the covalent appears to create the most energy advantage. In the high density all the electrostatic distances are lower yet it is as higher energy. Below is a practical use by cells for this difference in energy. The energy is high enough in the water to turn cells off and on.

 

ScienceDirect - Cell Biology International : HIGH AND LOW DENSITY WATER AND RESTING, ACTIVE AND TRANSFORMED CELLS

 

Resting and active states of cells are described in terms of the expectation, derived from experiments with aqueous polymers, that they contain two modified forms of water: high density, reactive, fluid water and low density, inert, viscous water. Low density water predominates in a resting cell and is converted to high density water in an active cell. It is proposed that switching from one state to another is an integral part of cellular function. When this ability is lost cells are transformed either to a state of rigor or to a hyperactive state in which they no longer depend upon external signals.

 

Low density tetrahedral water can freeze cells into inactivity because it does not provide enough energy to get everything into gear. If we froze the DNA, at room temperature, with low density water, it would become sluggish. If you want mutations you need high density water near the DNA, to give the DNA an extra energy boost.

[dkv]

Interesting but should happen with other different types of liquids as well.

The high internal energy is used to reach to the lower energy levels by the molecules and the atoms.In other words atoms borrow energy internally to do this magnificient act.

[alexander]

yes it should, but it largely would depend on the viscosity of the liquid, and it would be dependent on a couple of values for the liquids, namely:

density of the cooler liquid should be less then density of the hotter (aka it should sink to form the convection current we are looking to get)

there should be a significant value for the amount of energy it takes to produce vapor for that liquid, significant, and yet enough so the atoms can still get loose in a warm liquid

the value of energy used to produce vapor should be higher then the energy needed to solidify the liquid

and once again density should be fairly high, i'd imagine, actually i dont think it matters, as long as it increases as the liquid cools, to create the desired effect :)

 

i'd imagine you would get this result with alcohols as well, but they are very similar to water... i wouldn't be the person to advise, perhaps someone more competent should do it, but i am sure this is not uncommon in other liquids

[dkv]

The water has more than 15 different sturctures.. and has more than 60 anomalies.

In this case the at higher temperature the molecules get the super highway to cool faster. Geometrical rearrangement is a complex process. It should be possible to observe such anomalies with amino acids and proteins.