Wolfram
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How much of water is empty space?
How big procentage of the water volume of water are consists of atoms and how big procentage is the empty space between the water molecules?
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Levi
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Well, 1 gram of water molecules take up about 1cm<sup>3</sup> and the approx molar mass of a water molecule is 18 g/mol. Therefore there
are about warning: math ahead 1g*(mol/18g)*(6.022e23 molecules/mol) = 3.346e22 water molecules bouncing around in 1 cubic cm of
space. If anyone happens to know the approx size of an O and H atom you can figure out how much of that cubic cm is actually water. I'm too lazy to
look it up.
Chemcrime does not entail death. Chemcrime is death.
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Furch
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As I see it, it's a trick question... As I understand it, there is no matter in the sense that we think about it.
They say that the distance between a hydrogen atoms nucleus and its electron is proportionate to the distance between the earth and the moon, or the
sun, I forget.
Point being, that there is more "nothing" than there is "something" in a mole of any substance, be it in solid, liquid or gaseous form.
\"Those who say do not know, those who know do not say.\" -Lao Tzu
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woelen
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An atom is 99.9999999999...% empty space. The nucleus is increadibly small compared to the size of the orbitals (whatever one would imagine with the
orbitals).
So, the question of how much empty space exists in water is ambiguous. If you regard all space inside the said orbital radii as being part of atoms,
then one could say that a few tens of percent of space is empty. If only space, occupied by the electrons and nuclei is regarded as being part of the
atom, then the amount of empty space is almost 100%.
Space, really filled up with matter exists in neutron stars. Such matter is intensely dense, something like a few million tons per cm³.
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Furch
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Also, investigating the atom nucleus further, you will find subatomic particles (neutrons and protons, quarks etc.), and as far as I know there is
nothing that proves or even suggests that these are made up of a "solid" substance. So there is a risk that indeed 100% of everything we know as solid
is not. Rather some other variation of energy.
\"Those who say do not know, those who know do not say.\" -Lao Tzu
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Wolfram
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I dont know what you are talking about atoms are very very small tennis balls as I know it.
[Edited on 23-2-2007 by Wolfram]
[Edited on 23-2-2007 by Wolfram]
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Levi
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| Quote: | Originally posted by Wolfram
I dont know what you are talking about atoms are very very small tennis balls as I know it. |
I agree. Always have been and always will be.
Anyhow, a more practical question might be: "What is the distance between two adjacent water molecules at STP?" You can then specify that you want
the measurement to be made from the center of mass of each molecule.
I think the answer is something like: 1/(3.346e22<sup>1/3</sup>cm but
I'm not sure how hydrogen bonding affects the answer as that solution assumes the space between all adjacent molecules is the same. This is of course
untrue regardless of H-bonding since the "temperature" of some molecules is much greater than that of others... Hmm--lots of stuff to think about
with this question. Any particular reason you're asking?
[Edited on 23-2-2007 by Levi]
Chemcrime does not entail death. Chemcrime is death.
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12AX7
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Ooh, I can do this!
Well, what's the molecular weight of water? About 18g/mol, or 18g per 6.03 x 10^23 molecules. 1g = 1ml H2O (at some temperature), so that's 6.03e23
/ 18 molecules per ml.
Since hydrogen bonds (or other liquid bonds, if you want to talk about different condensed matter) are constantly reforming every picosecond, it's
meaningless to talk about anything specific; only statistical averages apply, which are fine. Kind of a quantum mechanical blurryness, which there
ought to be at this scale.
If I assume the density is even (it better be, at least on a macroscopic, averaged scale, and presumably of zero ionic strength or something), the
volume per molecule should be the reciprocal, or 18/6.03e23 ml/molecule (obviously, mililiters are woefully large to express this volume ). The dimension per side, then, is the cube root, or (converting ml to cm^3), 3.1 x
10^-8 cm or 0.31 nanometers per molecule. This sounds like a pretty reasonable intermolecular distance.
Tim
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chemrox
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all of it: matter is a thought
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unionised
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When liquid water freezes it expands by about 10% so, compared to the solid, about minus 10% of it must be space.
[Edited on 25-2-2007 by unionised]
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vulture
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| Quote: |
0.31 nanometers per molecule. This sounds like a pretty reasonable intermolecular distance. |
Nope. An average hydrogen bond in water is about 1.97 Aengstrom which is 0,197 nm.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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woelen
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But the order of magnitude is indeed reasonable. The kind of calculations, done by 12AX7, only is very rough, but it is the kind of calculations,
which gives insight in the order of magnitude of certain quantities and as such has great value.
Speaking of 'intermolecular distance' of course is somewhat ambiguous (but 12AX7 also said something like that), simply because of the irregular shape
of the molecules, and also for the reasons stated by 12AX7.
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12AX7
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Yeah, I can imagine that it'd be about half that considering the molecule is long and tends to orient with nearby dipoles -- that is, the hydrogen
bond. On average, how many hydrogen bonds are there, anyway? They're constantly changing (except in ice). Also, is the hydrogen bond distance from
H to nearby O (or O's lone pair orbitals) or center to center of the water?
My model assumes the molecules take up a cubic volume, which is obviously erroneous, but it's a lot easier than assuming spheres or three blobs of
some geometry and working out the packing for them. Works out the same on the average, anyway, which is about all that matters in an entropy-rich
liquid.
As a physicist, it is my business to make SWAGs and do the math in my head or on any nearby envelopes (OK, to do the scientific notation I used a
calculator above). Chemists are just being anal (and I don't mean "analytic") when they want something like this to 9 decimal points.
Tim
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Mr. Wizard
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Define "empty space", and the size space you are looking at.
[Edited on 25-2-2007 by Mr. Wizard]
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Nerro
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The space between the outer electrons and the nucleus is hardly empty space. It's littered with electrons that (together) need all that space. At any
given moment it might be mostly empty space but that's not at all a realistic representation of an atom.
#261501 +(11351)- [X]
the \"bishop\" came to our church today
he was a fucken impostor
never once moved diagonally
courtesy of bash
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woelen
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Well, if it is not empty space, then you could indeed say that the electrons are smeared out over a certain amount of space, but the reasoning is
equivalent, then this smearing out can be regarded as a ultra-low density distribution of the electron over space. The electrons in their orbitals can
be regarded as a spatial density distribution, both for charge and for mass.
You'd better say then that every point in space is 99.99999999...% empty space with a little bit of electron (and nucleus) in it. Fact remains that
our normal matter (atoms, electrons) is increadibly low-density in terms of spatial occupation. Neutron stars demonstrate that matter can be condensed
extremely, but the Pauli exclusion principle assures that this does not occur under normal conditions (electrons can't occupy same orbitals with same
spin). Only, when they are destroyed by 'melting down' with the nucleus (as in the enormous pressure of a super nova explosion), this exclusion
principle does not hold because the electrons are no more. The exclusion principle still holds, but at a lower level (the neutrons also cannot occupy
the same 'orbitals'). When pressure further increases, then the neutrons also collapse, and there is no other form of matter, which by means of a
Pauli-exclusion principle prevents further collapsing. From that point collapsing continues for ever, leading to formation of a black hole.
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apidej
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thank you ,very good
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evil_lurker
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How much of water is empty space?
I'm going to take the easy route on this one... 0%
One could take into consideration molecualar diameters and all that theoretical mathmatical gobbledygook but its all relative because if I
dive into a swimming pool, I'm not diving into empty space, I'm diving into water.
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12AX7
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On the average yes, but then again, nothing compared to neutronium, so there's always some absolute value important. Zero is always a good one.
Another question: how much of space is empty space? Counting mass-energy, of course.
Tim
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