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Name:   Mtchel W. E.
Status:  other
Age:  40s
Location: N/A
Country: N/A
Date: 2000


Question:
As temperature drops the density of water increases until at about 34 degrees farenheit it reaches its maximum density. as the temperature falls still further then the density of water then decreases as it approaches freezing. So you could say that at both around 33 degrees and at 35 degrees the density of water is the same, yet something is different about those two waters. Is it that the shape of the molecules at those two temperatures is different but equal in size, or is something else going on? I am not sure where this leads but I shall tell you where it took my imagination. I have felt that maybe at those temperatures the bonds in those molecules can be more easily shifted, perhaps liberating energy, or perhaps at these low almost freezing temperatures natural cleavage points are present which would enable easier seperation into hydrogen and oxygen. so that perhaps by performing hydrolysis at maximum density at 34 degrees, while lowering the temperature to 33 drgrees or perhaps even to freezing, would allow the heat of freezing energy to be somehow used to enhance the hydrolysis with an energy surplus, or maybe there is a cleavage point at the low temperature and increaseing density of 33 degrees that allows changing the shape of the bonds to release energy. perhaps some experiments could be done in an mri machine using radio waves to alter the bonds of 33 degree water and 35 degree water and to see if they can be shifted back and forth with ease. for although 33 and 35 degree waters are not isomers but are maybe just slightly different in bond positions, it might be enough of a diffeerence that a small change in the electromagnetic field applied externally chan mutate one water to the next while skipping the 34 degree maximum density. if 35 degree water could be shifted instantaneously to 33 degree water with little imput. in another direction , 34 degree water at maximum density


Replies:
Water is an intensely-studied liquid, yet much about its structure remains unknown. HOwever, I believe that enough is know to be able to answer your question. The dip in specific volume of water with temperature is the result of two competing tendencies: (1) the higher degree of order between water molecules as the temperature decreases, resulting in a more open, high-volume (low-density) configuration, and (2) the faster motion of the water molecules as the temperature increases, forcing the molecules farther apart. Property (1) is an unusual property of water, arising from its preferred tetrahedral arrangement of hydrogen bonds. This leads to a solid (ice) that is less dense than the liquid, which is unlike most other substances.

The temperature of maximum density simply is the point at which the contraction due to decreased thermal motion is not outweighed by the increased order and ice-like structure of liquid water. So although the average spacing between water molecules at 33 and 35 degrees F are the same, the relative orientations of the molecules, and their velocities, are different.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois



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