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Warren Platts
2007-Oct-18, 02:28 PM
I know that an adiabatic process is one without external sources of energy. For example, the interior of Jupiter is sometimes said to be assumed to have an adiabatic profile--does this just mean that all chemical species are at equilibrium? But what about the Sun? Is the Sun an adiabatic system? What would a nonadiabatic profile be like?

alainprice
2007-Oct-18, 02:35 PM
My background is speaker design. In a closed volume of air, it is adiabatic when the speaker compresses and rarefracts the air. I always understood adiabatic to mean a change in pressure, which changes temperature(without the need for heat transfer).

I must have missed the true definition.

edit: non adiabatic is likely isothermal.

grant hutchison
2007-Oct-18, 03:25 PM
An adiabatic system is one that is energetically isolated: there's no net flow of energy across the boundaries of the system. I don't think chemical equilibrium is relevant to the definition.
Isothermal systems are one specific example of non-adiabaticity: heat flows across the system boundary in order to maintain a constant temperature. But of course any sort of energy transfer makes a system non-adiabatic.
I've encountered the concept most often in atmospheric physics. A rising, effectively adiabatic, parcel of air necessarily cools as it expands, since the expansion is driven by its internal energy; a falling parcel warms. An adiabatic atmosphere would therefore have a characteristic decline in temperature with height: the adiabatic lapse rate.
This has relevance to the convective stability of real atmospheres, which deviate from adiabatic temperature profiles in many different ways.

Grant Hutchison

Ken G
2007-Oct-18, 04:47 PM
An adiabatic system is one that is energetically isolated: there's no net flow of energy across the boundaries of the system.Careful, that can be misinterpreted in a fatal way. I means there's no transfer of heat across the boundary, which is a spontaneous reversion to a more likely configuration by randomly sharing energy. But the system does not need to be energentically isolated, in the sense that it can exchange work with its surroundings. Thus adiabatic expansion is not energy conserving within the expanding gas, or the expanding cosmic microwave background for that matter-- it does work and loses energy when it expands.

John Mendenhall
2007-Oct-18, 05:13 PM
Here's the Wiki article.

http://en.wikipedia.org/wiki/Adiabatic_process

This is definitely headache material. Anytime they start off by saying 'This can never happen in the real world, but it's a good approximation in many cases' then you know you're in trouble.

grant hutchison
2007-Oct-18, 06:05 PM
Careful, that can be misinterpreted in a fatal way.Yikes. Thanks. :)
Otherwise there would be no such thing as adiabatic work.

Grant Hutchison

PS: It was kind of you not to come straight out and say I was wrong. But I was wrong.

Ken G
2007-Oct-18, 08:46 PM
Well, you did correctly point out that expanding gas cools, and that's the work part, so you had the spirit of it right. Perhaps one more interesting point to make about adiabatic processes is that they conserve entropy so are reversible. One way to think of that is that adiabatic processes in effect "label" the gas by its entropy, since the entropy can't change if there's no heat transfer-- no more likely configurations are ever found by the system. That also means that when you have convection, as for that adiabatic lapse rate, all the gas is so mixed up that it all has the same entropy everwhere. The labels are all mixed, none of the gas has a noticeably different history-- each is just at a different moment in that shared history.

grant hutchison
2007-Oct-19, 11:12 AM
Well, you did correctly point out that expanding gas cools, and that's the work part, so you had the spirit of it right.Yeah, I think I understand it at least slightly better than my alleged explanation would suggest. I've no idea why I settled on talking about "energy" rather than "heat". Pretty dumb, since I've just recently been reading about Joule's "mechanical equivalent of heat" experiments (the rotor in the insulated tank). The whole point of that rig was that it was an adiabatic system with work entering from the outside!

Grant Hutchison

Warren Platts
2007-Oct-19, 11:52 AM
So work can be done by an adiabatic system, as in internal combustion engines, I guess.

What about the release of latent heat, as when water vapor condenses to rain in a rising air mass. Would that kind of parcel of air be considered to be adiabatic?

grant hutchison
2007-Oct-19, 05:33 PM
What about the release of latent heat, as when water vapor condenses to rain in a rising air mass. Would that kind of parcel of air be considered to be adiabatic?Yes, that event marks the transition from the dry adiabatic lapse rate (for unsaturated air) to the moist adiabatic lapse rate (for saturated air). Once a rising parcel of air cools to its dew point, the latent heat from condensing water offsets some of the cooling by expansion, so the lapse rate is lower.

Grant Hutchison

Jerry
2007-Oct-19, 06:13 PM
So work can be done by an adiabatic system, as in internal combustion engines, I guess.

What about the release of latent heat, as when water vapor condenses to rain in a rising air mass. Would that kind of parcel of air be considered to be adiabatic?

The term Adiabatic defines the gas expansion or compression process. Expanding gas has less energy per mole after the expansion than before, and by the very definition of temperature, the gas becomes cooler. Latent heat enters into the picture by changing the expansion heating or cooling rate.

A good example is when you open a pop can that is very nearly 0degC. The pressurized gas leaves the can, and the remaining gas is much, much cooler - for a few milliseconds, the gas can be as cold as -40degC! (We used a high speed temperature sensing probe and actually measured this.) The heat from the surrounding metal, fluid and air quickly bring the temperature of the gas to dynamic equalibrium, but in the process, if the pop in the can was already less than 1degC, it may form a slurry.

Warren Platts
2007-Oct-19, 11:06 PM
Yes, that event marks the transition from the dry adiabatic lapse rate (for unsaturated air) to the moist adiabatic lapse rate (for saturated air). Once a rising parcel of air cools to its dew point, the latent heat from condensing water offsets some of the cooling by expansion, so the lapse rate is lower.

Grant Hutchison

The term Adiabatic defines the gas expansion or compression process. Expanding gas has less energy per mole after the expansion than before, and by the very definition of temperature, the gas becomes cooler. Latent heat enters into the picture by changing the expansion heating or cooling rate.
So let's say you were a weapons designer and were thinking of weather modification as a possible weapon, and so you wanted to design a powerful storm system, then, gentlemen, would not latent heat be good for that?

Kaptain K
2007-Oct-20, 04:26 AM
if the pop in the can was already less than 1degC, it may form a slurry.
The perfect temperature! :)

Warren Platts
2007-Oct-20, 02:08 PM
The perfect temperature! :)
I've often noted the same phenomenon occurring within beer cans as well. :D

grant hutchison
2007-Oct-21, 08:06 AM
So let's say you were a weapons designer and were thinking of weather modification as a possible weapon, and so you wanted to design a powerful storm system, then, gentlemen, would not latent heat be good for that?That's certainly what nature uses. :)

Grant Hutchison

mugaliens
2007-Oct-21, 02:45 PM
I know that an adiabatic process is one without external sources of energy. For example, the interior of Jupiter is sometimes said to be assumed to have an adiabatic profile--does this just mean that all chemical species are at equilibrium? But what about the Sun? Is the Sun an adiabatic system? What would a nonadiabatic profile be like?

From Merriam-Webster: "occurring without loss or gain of heat"

So, no, the sun's nuclear furnace isn't "adiabatic" in the slightest.

What's a "chemical specie?"

grant hutchison
2007-Oct-21, 03:07 PM
What's a "chemical specie?"Species: A kind, variety or type.

Warren Platts is talking of atoms, molecules, and ions of various degrees: all the kinds of things that do chemistry.
(The singular of this kind of species is species, BTW; specie is coinage.)

Grant Hutchison

Edit: The IUPAC's Gold Book provides a more detailed definition (http://www.iupac.org/goldbook/C01038.pdf) (pdf).

mugaliens
2007-Oct-21, 05:03 PM
Species: A kind, variety or type.

Warren Platts is talking of atoms, molecules, and ions of various degrees: all the kinds of things that do chemistry.
(The singular of this kind of species is species, BTW; specie is coinage.)

Grant Hutchison

Edit: The IUPAC's Gold Book provides a more detailed definition (http://www.iupac.org/goldbook/C01038.pdf) (pdf).

Are you absolutely positive about that, Grant?

From Merriam-Webster:

Main Entry: 1spe·cie
Pronunciation: \ˈspē-shē, -sē\
Function: noun
Etymology: from in specie, from Latin, in kind
Date: 1617

grant hutchison
2007-Oct-21, 05:12 PM
Are you absolutely positive about that, Grant?Yes.
In specie, the Latin phrase mentioned in your reference, has several meanings of its own.
Specie used to mean a type or kind of entity, is (to quote from the OED) "Now obsolete except as erroneous singular of species".

Grant Hutchison

Jerry
2007-Oct-21, 06:07 PM
So let's say you were a weapons designer and were thinking of weather modification as a possible weapon, and so you wanted to design a powerful storm system, then, gentlemen, would not latent heat be good for that?
You mean like pumping CO2 into the atmosphere to warm the ocean, then see what happens? I think you are describing a work in progress, and so far, the results have been very impressive: Eight category five hurricanes in five years!

Hurricanes form in a complex series of heat transfers; gravity and the coriolis effect to remove thermal energy from water and turn it into awesome kinetic energy in the atmosphere. But without the ocean heat reservoir, the storms die.

This is why I feel it is necessary to place an underlying heat source to create the great spot on jupiter. I'm guessing the focusing source is related Jupiters magnetic field, but it could be a large volcanic caldera or even a water vapor system. It is disheartening to see how little scientific energy is used to try to solve this mystery staring us right in the face.

Ken G
2007-Oct-22, 12:30 AM
In specie, the Latin phrase mentioned in your reference, has several meanings of its own.
Specie used to mean a type or kind of entity, is (to quote from the OED) "Now obsolete except as erroneous singular of species".


Are you then saying that the Merriam-Webster definition is specious?

grant hutchison
2007-Oct-22, 01:00 AM
Are you then saying that the Merriam-Webster definition is specious?:)
Same etymology there, again: from the Latin species, which refers to the outward appearance of things. The ablative singular is specie, giving us the phrase mugaliens quotes from Merriam-Webster, in specie, usually translated as "in kind"; that is, "in the same kind of thing". (The Oxford English Dictionary list nine different shades of meaning. How can you not love a dictionary that does that?)
But species has a different derivation, straight from the Latin nominative. Fifth-declension nominative singular and plural are identical, and (like series) species has managed to make it into English with that structure intact.

Grant Hutchison

astromark
2007-Oct-22, 03:23 AM
We seem to spend far to much effort on the proper and improper usage of this English language. When I saw the words 'chemical species' a deep furrow appeared across my balding head... I stopped myself leaping to the usual wrong conclusions and instead just watched you all do it for me. In the context used what was meant? I might have worded it differently as most of you would also. I sagest that I drew the proper conclusion from what I understood was meant. That elements in balance. No energy lost or gained.
Some people do not understand the complex ways in which language can be misused. Keep this up and I am learning.... and until this thread started I had never herd the term adiabatic. Now I know. Just what that had to do with the right temperature of bear ( Oops..beer. ) I will never know, ( but enjoy.).

Warren Platts
2007-Oct-22, 03:29 AM
But then, what is fusion but a sort of release of latent energy, is it not? Couldn't we think of the conversion of metallic hydrogen to helium as a sort phase change that takes place at the proper temperature and pressure?Probably not, because fusion is an irreversible process. Adiabatic reactions, phase changes, etc. should be completely reversible and depend only on the local pressure and temperature, right?

Michael Noonan
2007-Oct-22, 07:06 AM
Originally Posted by Warren Platts
But then, what is fusion but a sort of release of latent energy, is it not? Couldn't we think of the conversion of metallic hydrogen to helium as a sort phase change that takes place at the proper temperature and pressure?
In that case should we be detecting Čerenkov radiation of some sort given that it is then a nuclear process?

kzb
2007-Oct-22, 05:32 PM
"Chemical species" (can be singular or plural, i.e. there is no such thing as a "chemical specie") is a much used term in chemistry.

Along with "speciation", which is used a lot in environmental chemistry. For example, the element chromium can have several different species in the environment, Cr3+ which is cationic, or the anionic chromate ion (Cr04)2-.

It's important to know the species, as they have different properties and health implications.

loglo
2007-Oct-22, 07:39 PM
Are you then saying that the Merriam-Webster definition is specious?

Isn't specious the definition of "Merriam-Webster" in OED and vice versa?
:)

Warren Platts
2007-Oct-22, 09:24 PM
I was thinking of 'chemical species' as I read it in Jupiter: The planet, its satellites and magnetosphere, edited by Fran Bagenal, Timothy Dowling, and William McKinnon (2004, 10):


Observation of the planet's atmosphere indicates that several major chemical species (such as helium, and water) are partly sequestered into the interior.

kzb
2007-Oct-23, 05:08 PM
Warren Platts :
That seems to be a looser usage of chemical species than would be employed by most chemists. I suppose water might be considered a species of hydrogen or oxygen (although again this is uncommon usage). The species of helium is elemental helium (as it always is).

It is usually used in connection with different ionization or oxidation states, e.g. Fe2+ or Fe3+ in solution.

Everything except hydrogen is a 'metal' to astronomers, so I don't think we should be too surprised if the usage of 'chemical species' is a little eccentric too.

grant hutchison
2007-Oct-23, 05:45 PM
Warren Platts :
That seems to be a looser usage of chemical species than would be employed by most chemists.Unless I'm misreading or misunderstanding, it does seem to correspond to the usage given by the IUPAC Gold Book, which I linked to (http://www.iupac.org/goldbook/C01038.pdf) earlier:
An ensemble of chemically identical molecular entities that can
explore the same set of molecular energy levels on the time scale
of the experiment.where "molecular entities" are
Any constitutionally or isotopically distinct atom, molecule, ion, ion pair,
radical, radical ion, complex, conformer etc., identifiable as a separately
distinguishable entity.
Grant Hutchison

kzb
2007-Oct-24, 05:21 PM
Grant Hutchinson, I was only going by my experiences with environmental chemists:)

However on that same site we have:

chemical species (of an element)

Specific form of an element defined as to isotopic composition,
electronic or oxidation state, and/or complex or molecular structure.

That fits in with what I think is the most common usage.

grant hutchison
2007-Oct-24, 06:11 PM
Grant Hutchinson, I was only going by my experiences with environmental chemists:)For sure. I wasn't intending to suggest that you were wrong in what you were saying. But it did seem that Warren Platt's more general usage at least had some support from the Union of Pure and Applied Chemistry. :)

Grant Hutchison

Warren Platts
2007-Oct-25, 01:09 PM
A related question:

What's the difference between adiabaticity and superadiabaticity?

grant hutchison
2007-Oct-25, 01:18 PM
What's the difference between adiabaticity and superadiabaticity?In meteorology, a superadiabatic lapse rate prevails in a region of atmosphere in which the temperature falls faster with height that the dry adiabatic lapse rate.
It means that a rising parcel of air will tend to stay warmer than its surroundings, and so will continue to rise: there is convective instability.

Grant Hutchison