CharlesChandler wrote:
. . . a theorist has to pick his battles carefully -- somebody who fights everything that stands between him and his vision just might pick a fight with bedrock, and the bedrock always wins.
As concerns the atomic theory & laboratory confirmation related to
surface tension, he's probably going to lose that one.
Have you ever wondered why liquid H2O
is so fluid? If you look into the literature you will read that the H2O molecule
is a polar molecule. Reading further you will find an explanation along the lines that the H2O molecule possesses lopsided electronegativity and this causes the oxygen side
of the molecule to possess a slight negative charge. And it causes the dual positive ends, where the hydrogen atoms are covalently attached, to possess a slight positive charge. Reading even further you will find that this lopsidedness
of charge—it’s polarity—explains why H2O molecules clump together and why (for one example
of numerous properties
of H2O) it possesses such a high boiling temperature. But it occurred to me that if it
is this polarity that causes H2O molecules to possess this mutual attraction why
is it so fluid. Strangely, H2O remains very fluid throughout the whole temperature range
of its liquid phase. When I went looking for an explanation the only thing I could find indicated that the high fluidity
of liquid H2O
is one
of many
anomalies of H2O. An anomaly
is an observe behavior that
is inconsistent with or not predicted by theory. Most chemicals have have a handful
of anomalies. Usually a chemicals
anomalies occur only under extreme conditions. H2O
is anomalous with respect to having numerous
anomalies, upwards
of seventy, and many
of these happen right before our eyes.
Another of H2O’s
anomalies is surface tension. If you look closely at a water droplet you might notice a kind
of slumpiness to it. When hanging this slumpiness gives it a kind
of egg or pear shape. Resting on a
surface this slumpiness results in kind
of a pancaked aspect to it. If we were to try to create something that modeled this behavior we might stuff a balloon with sand. And if we were to then attempt to describe the physics associated with the sand filled balloon and its observed slumpiness we might draw attention to the fact that there are no tensional forces between the grains
of sand. All
of the tensional forces are associated with the stretched rubber
of the balloon that envelopes the sand. If we were to then apply this same reasoning to flesh out an analogue between a sand filled balloon and the water droplet we might find ourselves saying that there are no tensional forces between water molecules below the
surface of the droplet. All
of the tensional forces are associated with the interconnected matrix
of H2O molecules along the
surface of the water droplet. And therein we would find ourselves confronting a conceptual quandary. With the sand filled balloon the properties
of the balloon and the properties
of the sand are different. But with the water droplet the molecules below the
surface and the water molecules along the
surface are the same molecules and therefore could only have the same properties. Right?
Actually, that
is not right. There are two ways in which the H2O molecules along the
surface are distinctive from those below the
surface, but it
is the way that these two ways are themselves related that really gives us insight into the nature
of H2O polarity. Firstly, H2O molecules along the
surface are less interconnected than those below the
surface. This
is a consequence
of the two dimensional geometry
of a
surface making it harder for hydrogen bonds to be completed. Specifically, H2O molecules along the
surface are more likely to share one and only one hydrogen bond with a neighboring H2O molecule. In contrast, those below the
surface are more likely to share two hydrogen bonds with adjacent H2O molecules. This
is a consequence
of the three dimensional geometry below the
surface making it easier for H bonds to be completed. (If we were to use more technical terminology we would say that those along the
surface with only one H bond are tetrahedrally asymmetric [lopsided] while those below the
surface that possess two H bonds are tetrahedrally symmetric.)
This brings us to something that appears to be a dichotomy. Along the
surface hydrogen bonding
is less comprehensive yet it
is these bonds that provide the tensional forces that maintain the integrity
of the droplet. Below the
surface there are more hydrogen bonds yet there
is a general absence
of tensional forces existing between these molecules. This seems to not make sense. Our intuition tells us that if there are more bonds below the
surface and less bonds along the
surface that those along the
surface should result in structural weakness and those below the
surface should be stronger. But exactly the opposite
is the case, the
surface has fewer H bonds but these bonds are stronger, providing the
surface structural rigidity. Below the
surface there are more H bonds but these bonds are weaker, so weak in fact that there
is almost zero structural rigidity below the
surface.
The solution, I contend, starts with understanding that those along the
surface have greater polarity than do those below the
surface and polarity
is what determines the strength
of a hydrogen bond. And since those along the
surface have greater polarity the H bonds they share with neighboring H2O molecules are strong H bonds. Below the
surface the H bonds that are shared between the different H2O molecules are weak bonds because below the
surface the H2O molecules have very little polarity.
Why
is it, you may wonder, that water molecules that share only one H bond with an adjacent water molecule have polarity while those that have two have very little polarity? The answer, I contend,
is that H bonds between water molecules actually serve two functions. Firstly, and most obviously, they combine or connect two water molecules. Secondly, they neutralize each others polarity. One H bond neutralizes one half
of their polarity and two H bonds neutralize all
of their polarity. And since polarity dictates the strength
of bonds this
is why singular bonds along the
surface are strong bonds. Below the
surface there
is very little polarity (for reasons I won’t attempt to explain polarity never completely drops to zero) there
is little tensional strength. And that
is because the prevalence
of H bonds below the
surface has neutralize most
of the polarity.
So now we know why liquid H2O
is so fluid despite its polarity. It really isn’t a polar molecule when it
is in the liquid state because the prevalence
of H bonds has neutralized its polarity.
From this we also get a sense
of significant structural capabilities that emerge when the
surface area
of H2O
is maximized, as occurs on wind shear boundaries in the atmosphere:
http://www.thunderbolts.info/wp/forum/phpB ... 82#p117061
and
http://www.thunderbolts.info/wp/forum/phpB ... 85#p122282
Also, if you are interested in a quantum mechanical perspective on H2O polarity and hydrogen bonding go here:
http://www.thunderbolts.info/wp/forum/phpB ... 82#p117063
James McGinn / Solving Tornadoes