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Fred Kasner · Guest

Andrew Usher wrote:
[quote]On Jul 25, 6:55 pm, Fred Kasner <fkas...@sbcglobal.net> wrote:

I maintain that an equation written like
2 H2 + O2 -> 2 H2O + 584 kJ/mol
is actually incorrect, while
2 H2 + O2 -> 2 H2O + 6.05 ev
is perfectly clear.
You apparently never bothered to stay awake during the single college
chemistry course you took. The equation 2H2 + O2 -> 2H2O + delta H is
well understood to be a NOT a molecular equation but a molar equation

That>s ridiculous semantics. Moles are only meaningful BECAUSE
they correspond to a certain number (an arbitrary magic number) of
atoms or molecules.

wherein the statements are: 2 moles of H2 react with one mole of O2 to
produce 2 moles of water plus some specific amount of heate stated in
kilojoules (or as it used to be in kilocalories).

Molecules are reacting. Moles are not a physically meaningful
concept.

As you wrote it it is
ambiguous as you can>t tell whether the number of moles refers to the H2
or the H2O or refers to the O2. You are either stupid, or careless, or
ill educated.

So you agree with me, then call me stupid etc. ? Wow.

Andrew Usher
[/quote]
Obfuscation on your part and refusal to admit the use of practical
quantities does not an argument make. A mole is a counting artifice
similar to a dozen or a hundred or some other bunch invented for
convenience. You inability to accept such means that you are blinded by
artifices of equally arbitrary nature that you learned from physicists
who really wanted to be mathematicians. Even the molecule suffers from
arbitrariness. The wave function for a particle in a "molecule" is
infinite in extent but is too ephemeral to deal with as such and so the
approach of the chemist to deal with it as if it were a
nonelectromagnetic field but rather some fuzzy particle with reasonable
boundaries and em properties only when you are very close to it. It is
you who engage in ridiculous semantics. Since names and properties for
real things make them useful as opposed to pure numbers which are good
only for counting items.

It appears to all others that I do not agree with you at all. Your last
equation is perfectly acceptable as way to deal with chemical
reactivity. However if you want to deal with amounts of things that are
to few to even be visible then you have to deal with dozens, or gross,
or moles.
FK

Lloyd · Guest

On Jul 27, 5:27 pm, Andrew Usher <k_over_hb...@yahoo.com> wrote:
[quote]On Jul 27, 3:23 am, schu...@mail.biu.ack.il (Richard Schultz) wrote:

In sci.chem Andrew Usher <k_over_hb...@yahoo.com> wrote:

: Really, so if the SI standards are the final arbiter of what>s
: fundamental ...
:
: a) what is the physical significance of the candela?

AFAIK, it cannot be derived from the other six fundamental units.

Avoiding the question.

: b) is current more fundamental than charge?
:
: (The answers are obviously none and no.)

In any system of units, one can define either a unit of current or a unit
of charge, in which case the other can be derived from the defined unit.

Avoiding the question.

The Kelvin is a "fundamental" unit because it cannot be derived from the
other six fundamental units.

Wrong. It is equal to 1.380650e-23 J. Ir has to be.

[/quote]
Uh, according to the CGPM, a K is: The kelvin, unit of thermodynamic
temperature, is the fraction 1/273.16 of the thermodynamic temperature
of the triple point of water.

Nothing about joules.

And I think the CGPM has a little more authority than you.

[quote]ENTROPY IS MATHEMATICALLY DEFINED TO BE A PURE NUMBER.
[/quote]
Can>t be. 10 g of O2 has a more entropy than 5 g. You>ve got to have
some numerical scale for reference so the units are the same,
otherwise you can make up any number.

See http://physics.nist.gov/cuu/Units/units.html -- the NIST doesn>t
agree with you.

[quote]Since mathematics is prior to physics or chemistry, arguing with this
is stupid, ignorant, or insane.

:> This news will also come to a big surprise to anyone who has studied
:> thermodynamics and/or statistical mechanics.
:
: Not to anyone who understood them.

Anyone who understands statistical mechanics knows that it is possible to
determine the energy of a single particle, but that it is meaningless to
even speak of the "temperature" of a single particle, temperature by
definition being a property of an ensemble of particles.

I don>t speak of the 'temperature' of a signle particle. But the
temperature
in a system _is_ related to average energies per particle.

Andrew Usher[/quote]

Andrew Usher · Guest

On Jul 29, 12:24 pm, Lloyd <lpar...@emory.edu> wrote:

[quote]The Kelvin is a "fundamental" unit because it cannot be derived from the
other six fundamental units.

Wrong. It is equal to 1.380650e-23 J. Ir has to be.

Uh, according to the CGPM, a K is: The kelvin, unit of thermodynamic
temperature, is the fraction 1/273.16 of the thermodynamic temperature
of the triple point of water.
[/quote]
That>s exactly the same thing.

[quote]And I think the CGPM has a little more authority than you.
[/quote]
No one has authority over the laws of nature.

[quote]ENTROPY IS MATHEMATICALLY DEFINED TO BE A PURE NUMBER.

Can>t be. 10 g of O2 has a more entropy than 5 g.
[/quote]
Of course it has twice as much. That doesn>t say anything
about the units of entropy.

S = -sum(p log p) . No units in there.

[quote]Since mathematics is prior to physics or chemistry, arguing with this
is stupid, ignorant, or insane.

[/quote]
Andrew Usher

Richard Schultz · Guest

In sci.chem Andrew Usher <k_over_hbarc@yahoo.com> wrote:

:> > > The Kelvin is a "fundamental" unit because it cannot be derived from the
:> > > other six fundamental units.

:> > Wrong. It is equal to 1.380650e-23 J. Ir has to be.

:> Uh, according to the CGPM, a K is: The kelvin, unit of thermodynamic
:> temperature, is the fraction 1/273.16 of the thermodynamic temperature
:> of the triple point of water.

: That>s exactly the same thing.

I>ve never quite understood why some people get so much enjoyment out
of publically displaying their ignorance.

-----
Richard Schultz schultr@mail.biu.ac.il
Department of Chemistry, Bar-Ilan University, Ramat-Gan, Israel
Opinions expressed are mine alone, and not those of Bar-Ilan University
-----
"You don>t even have a clue about which clue you>re missing."

Andrew Usher · Guest

On Jul 30, 10:35 pm, schu...@mail.biu.ack.il (Richard Schultz) wrote:
[quote]In sci.chem Andrew Usher <k_over_hb...@yahoo.com> wrote:

:> > > The Kelvin is a "fundamental" unit because it cannot be derived from the
:> > > other six fundamental units.

:> > Wrong. It is equal to 1.380650e-23 J. Ir has to be.

:> Uh, according to the CGPM, a K is: The kelvin, unit of thermodynamic
:> temperature, is the fraction 1/273.16 of the thermodynamic temperature
:> of the triple point of water.

: That>s exactly the same thing.

I>ve never quite understood why some people get so much enjoyment out
of publically displaying their ignorance.
[/quote]
You should be calling Lloyd 'ignorant', not me. I>m sorry that you
refuse to accept statistical mechanics, but it doesn>t change
the facts.

Fundamental equations should be written without spurious
constants. Yes, they can be, but teaching thermodynamics
using Boltzmann>s constant is like teaching mechanics
using pounds-mass and pounds-force and therefore writing

F = ma/g

as the 'fundamental' equation of force.

Andrew Usher

Craig · Guest

On Jul 30, 4:20 pm, Andrew Usher <k_over_hb...@yahoo.com> wrote:
[quote]On Jul 29, 12:24 pm, Lloyd <lpar...@emory.edu> wrote:

The Kelvin is a "fundamental" unit because it cannot be derived from the
other six fundamental units.

Wrong. It is equal to 1.380650e-23 J. Ir has to be.

Uh, according to the CGPM, a K is: The kelvin, unit of thermodynamic
temperature, is the fraction 1/273.16 of the thermodynamic temperature
of the triple point of water.

That>s exactly the same thing.
[/quote]
No, it is not. Andrew, I understand what you>re trying to assert.
You want temperature to have dimensions of energy, since temperature
is proportional to the average kinetic energy of an ensemble of
molecules. Why can>t that proportionality constant be unitless? The
problem is, that "constant" of proportionality is not constant for all
substances!

Here is one simple example. An ideal monatomic gas has <E> = 3/2 kT.
However, if we consider a diatomic gas, now some of that energy can be
not only translational motion but also rotation about two axes, giving
<E> = 5/2 kT. If T is high enough, the vibrational motion between the
atoms may also be excited, for an even higher value. Another way of
saying this is that heat capacity is not the same for all substances.
For added joy, heat capacity is, in general, a function of
temperature. So, how much energy does a substance a temperature T
hold? (Let>s assume our reference/"zero" is zero Kelvin.) The best
answer is [integral]C(T)dT. In general, this is NOT a simple
proportionality. So, the total internal energy of a balloon of helium
and an identically sized balloon of, say, nitrogen, will be different,
even at the same temperature. If you place these hypothetical
balloons in thermal contact, they will exchange heat until their
*temperatures* are the same, not their total internal energy. How
much energy does one degree Kelvin represent? Clearly, the answer
must be, "it depends."

[quote]And I think the CGPM has a little more authority than you.

No one has authority over the laws of nature.
[/quote]
True, but the standards were not established lightly, nor without
careful thought.

- Craig

PD · Guest

On Jul 24, 7:11 pm, Andrew Usher <k_over_hb...@yahoo.com> wrote:
[quote]In science, I have always thought, equations benefit by being as
simple
as possible, without extraneous 'magic numbers'. This is a
justification
given for choosing the maetic system over English units (when a
rational
justification is used at all for that). And yet, Boltzmann>s constant
is
clearly such a 'magic number'.
[/quote]
Actually, the metric system has a substantial amount of unnecessary
baggage as well. For example, there is no earthly reason why the speed
of light should be anything other than 1 and unitless. And indeed,
there are a number of variations of "natural units" which make as many
constants as possible disappear from laws of physics. A simple
Wikipedia search will illuminate.

However, you will note that it is not possible to come up with a
system of units where *all* of the constants relevant in natural laws
will disappear. It is certainly possible to choose one such that
Boltzmann>s constant will disappear, but at the expense of another non-
unity constant appearing elsewhere.

PD

[quote]
For example, I write the Boltzmann function

f(E) = exp(-E/T)

where the standard way would be

f(E) = exp(-E/kT)

and the k serving as a meaningless constant or conversion factor.

More than that, it affects the notion of entropy, which is really
fundamental. More than physics, actually - entropy is a mathematical
concept at root, and therefore is always dimensionless. And yet,
idiot
thermodynamics force us to write 'J/mol-K'; as if those units matter
one
bit. Presenting a dimensionless number as otherwise is positively
misleading.

Heat capacity is also unitless, at least if measured on a molecular
basis, which is preferable at least for gases. I have given the
criterion
for convective stability

d log T / d log P = - 1/Cp

and this works only if Cp is dimensionless. Not only is this the
simplest
possible form but it expresses without words why it is correct, if
one
only looks at it.

Avogadro>s number is similar, and I believe things should never be
measured on a molar basis when they can reasonably be done on a
molecular
basis. The heats on chemical reactions, for example, can be given in
molecular units just as sensibly as in molar units. Indeed, electron
volts are already used for related purposes often by astrophysicists,
and
the band gap of solids is normally given in ev, and that is a
sort of chemical reaction. That unit also has a particular advantage
that
it is also used for the energy of photons, and therefore one can
correlate the two without the need of any conversion factor.

Andrew Usher[/quote]

Lloyd · Guest

On Jul 30, 7:20 pm, Andrew Usher <k_over_hb...@yahoo.com> wrote:
[quote]On Jul 29, 12:24 pm, Lloyd <lpar...@emory.edu> wrote:

The Kelvin is a "fundamental" unit because it cannot be derived from the
other six fundamental units.

Wrong. It is equal to 1.380650e-23 J. Ir has to be.
[/quote]
So you>re saying a fundamental unit is based on a derived unit.
Circular logic mean anything?

[quote]
Uh, according to the CGPM, a K is: The kelvin, unit of thermodynamic
temperature, is the fraction 1/273.16 of the thermodynamic temperature
of the triple point of water.

That>s exactly the same thing.
[/quote]
So what are the units on deg C? Is it also J? Can>t be, as an object
can>t have a T with 2 different values, both in J. And if not, how do
you change the units going from K to deg C?

And what do you do with heat capacity? If you add 200 J to 100 g of
iron and 200 J to 100 g of water, they come to different temperatures.

[quote]
And I think the CGPM has a little more authority than you.

No one has authority over the laws of nature.

ENTROPY IS MATHEMATICALLY DEFINED TO BE A PURE NUMBER.

Can>t be. 10 g of O2 has a more entropy than 5 g.

Of course it has twice as much. That doesn>t say anything
about the units of entropy.
S = -sum(p log p) . No units in there.

Since mathematics is prior to physics or chemistry, arguing with this
is stupid, ignorant, or insane.

Andrew Usher[/quote]

Andrew Usher · Guest

On Jul 31, 2:54 pm, PD <TheDraperFam...@gmail.com> wrote:

[quote]However, you will note that it is not possible to come up with a
system of units where *all* of the constants relevant in natural laws
will disappear. It is certainly possible to choose one such that
Boltzmann>s constant will disappear, but at the expense of another non-
unity constant appearing elsewhere.
[/quote]
This is not true, as SI is already such a system, if temperature
were measured in Joules. No additional constants would appear!

Andrew Usher

Andrew Usher · Guest

On Jul 31, 3:04 pm, Lloyd <lpar...@emory.edu> wrote:

[quote]The Kelvin is a "fundamental" unit because it cannot be derived from the
other six fundamental units.

Wrong. It is equal to 1.380650e-23 J. Ir has to be.

So you>re saying a fundamental unit is based on a derived unit.
Circular logic mean anything?
[/quote]
That>s not circular, since the Joule involves only _other_ base
units (meter, kilogram, second).

[quote]So what are the units on deg C? Is it also J? Can>t be, as an object
can>t have a T with 2 different values, both in J. And if not, how do
you change the units going from K to deg C?
[/quote]
Celsius is not strictly a unit at all, as it is not an absolute
scale, of course. An object has only one temperature in J
or any other unit. Everyone knows how to convert C to K.

[quote]And what do you do with heat capacity? If you add 200 J to 100 g of
iron and 200 J to 100 g of water, they come to different temperatures.
[/quote]
They do, and what of it? This has nothing to do with the units
of heat capacity, which is dimensionless.

Andrew Usher

Craig · Guest

On Jul 31, 6:01 pm, Andrew Usher <k_over_hb...@yahoo.com> wrote:
[quote]On Jul 31, 3:04 pm, Lloyd <lpar...@emory.edu> wrote:
And what do you do with heat capacity? If you add 200 J to 100 g of
iron and 200 J to 100 g of water, they come to different temperatures.

They do, and what of it? This has nothing to do with the units
of heat capacity, which is dimensionless.
[/quote]
This is precisely the problem with trying to treat temperature as
having the dimensions of energy.

Suppose you add 200 J to 100 g of water. Suppose you have chosen a
scale such that this represents a change of "2 J" in water temperature
(since we have 100 g). Now, add 200 J to 100 g of iron (which has
approximately a tenth the heat capacity of water). This would raise
the temperature of the iron about 10 times as much. So, now the same
200 J causes a rise of "~20J" of iron temperature? The same amount of
energy gets converted into more "iron joules" than "water joules".
This clearly violates conservation of energy.

Suppose you add 20 J to 1 g of water. Suppose you have chosen a scale
such that this represents a change of "20 J" in water temperature.
Now, add 20 J to 10 g of water. The temperature rise will be 1/10 as
large. Will you now claim that 20 J of heat turns into only 2 J of
temperature? How can "heat joules" and "temperature joules" possibly
mean the same thing?

This becomes an untenable proposition. Temperature simply doesn>t
behave the same way energy does.

- Craig

PD · Guest

On Jul 31, 7:57 pm, Andrew Usher <k_over_hb...@yahoo.com> wrote:
[quote]On Jul 31, 2:54 pm, PD <TheDraperFam...@gmail.com> wrote:

However, you will note that it is not possible to come up with a
system of units where *all* of the constants relevant in natural laws
will disappear. It is certainly possible to choose one such that
Boltzmann>s constant will disappear, but at the expense of another non-
unity constant appearing elsewhere.

This is not true, as SI is already such a system, if temperature
were measured in Joules. No additional constants would appear!

Andrew Usher
[/quote]
Well, since you didn>t take the time to read up on natural units, let
me try one more tack.
In thermodynamics, there are intrinsic variables and extrinsic
variables, with the latter depending on the amount of "stuff" and the
former not. Temperature is an intrinsic variable, and energy is
extrinsic. Two reservoirs of identical material can have a common
temperature and be in thermal equilibrium, but have much different
internal energies. (As another example, mass is extrinsic while
density is intrinsic; a spring constant is extrinsic while Young>s
modulus is intrinsic.)

The joule is a unit of energy and so is a unit of an extrinsic
quantity. The kelvin is a unit of temperature and so is a unit of an
intrinsic quantity.

So if you chose temperature to have units joules, so that the relation
PV=nRT would become PV=nT (with R rendered to be 1 mole^-1), on the
left side you would have an *extrinsic* energy PV in joules and on the
right you would have an *intrinsic* quantity T in joules, with the
connection between the extrinsic joules and the intrinsic joules being
n the number of moles.

This seems to be a very odd way to do things, with joules referring to
two completely different kinds of quantities.

PD

Andrew Usher · Guest

On Jul 31, 7:58 pm, PD <TheDraperFam...@gmail.com> wrote:

[quote]In thermodynamics, there are intrinsic variables and extrinsic
variables, with the latter depending on the amount of "stuff" and the
former not. Temperature is an intrinsic variable, and energy is
extrinsic. Two reservoirs of identical material can have a common
temperature and be in thermal equilibrium, but have much different
internal energies. (As another example, mass is extrinsic while
density is intrinsic; a spring constant is extrinsic while Young>s
modulus is intrinsic.)
[/quote]
This is all right.

[quote]The joule is a unit of energy and so is a unit of an extrinsic
quantity. The kelvin is a unit of temperature and so is a unit of an
intrinsic quantity.
[/quote]
No, both are units of energy, and therefore could be used
either way.

[quote]So if you chose temperature to have units joules, so that the relation
PV=nRT would become PV=nT (with R rendered to be 1 mole^-1), on the
left side you would have an *extrinsic* energy PV in joules and on the
right you would have an *intrinsic* quantity T in joules, with the
connection between the extrinsic joules and the intrinsic joules being
n the number of moles.
[/quote]
The last word should be 'molecules'.

The form I actually prefer is P = rho T where rho is the number
density.
That>s even simpler, and illustrates the truth that pressure is a kind
of
energy density.

[quote]This seems to be a very odd way to do things, with joules referring to
two completely different kinds of quantities.
[/quote]
They can be considered two different kinds, but still have the
same dimension. Like, say, pressure and energy density. Or
temperature and change in temperature.

Of course, I actually state temperatures in electron volts,
rather than joules. This is due to its more convienient size,
use to measure atomic/molecular energy quantities, and
its use in the literature to state temperatures in certain
situations (whereas kJ/mol or cm^-1 are never so used).

Andrew Usher

Andrew Usher · Guest

On Jul 31, 7:55 pm, Craig <cager...@aol.com> wrote:

[quote]This is precisely the problem with trying to treat temperature as
having the dimensions of energy.
[/quote]
No, you are confused. See below.

[quote]Suppose you add 200 J to 100 g of water. Suppose you have chosen a
scale such that this represents a change of "2 J" in water temperature
(since we have 100 g). Now, add 200 J to 100 g of iron (which has
approximately a tenth the heat capacity of water). This would raise
the temperature of the iron about 10 times as much. So, now the same
200 J causes a rise of "~20J" of iron temperature? The same amount of
energy gets converted into more "iron joules" than "water joules".
This clearly violates conservation of energy.
[/quote]
This is not how temperature works! You can>t divide Joules
by grams and get Joules! Actually, you>d need to divide the energy
by the heat capacity, then by the number of atoms or molecules
(more generally, formula units) to get the change in temperature.

Andrew Usher

Andrew Usher · Guest

On Jul 31, 8:45 pm, Matthew Johnson <matthew_mem...@newsguy.org>
wrote:
[quote]In article <221a7beb-e33e-496d-96d4-d56f6e1f3...@59g2000hsb.googlegroups.com>,
Craig says...

[snip]

This becomes an untenable proposition. Temperature simply doesn>t
behave the same way energy does.

Not only that, but temperature>s units are reciprocal to those of energy. This
is clear from the modern, quantum mechanical definition as:

1/T = partial derivative of E w.r.t. Entropy.
[/quote]
Wrong way around, 1/T = dS/dQ.

[quote]Entropy, as the number of accessible quantum states, is dimensionless.
[/quote]
Actually the logarithm of the number of states, but yes (as logs are
always dimensionless).

Andrew Usher


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