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Author Topic: How is water heated?  (Read 14030 times)

Offline mxplxxx

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How is water heated?
« on: 31/05/2014 06:13:10 »
Pretty basic question I know "how is water heated?" but I don't actually have an answer. Presumably via "heat" photons (does such a beast exist?). So what do the heat photons interact with? With the hydrogen atom, with an electron, with an oxygen atom? With a quark within one of the atoms? Given its quantum nature, the photon cannot interact with more than one of these at once. So we have (say) a hydrogen atom that has been energised via a photon. How does this affect the water molecule as a whole? What does energised mean anyway. If speeded up, how can it do so given that it is constrained by molecular forces? What determines which atom/electron the heat photon interacts with? Why does a "heat" photon not pass through the water molecule as a light photon does? I await with interest for some replies.

« Last Edit: 31/05/2014 06:15:08 by mxplxxx »


 

Offline CliffordK

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Re: How is water heated?
« Reply #1 on: 31/05/2014 18:57:45 »
There are many types of heating & heat transfer.

Conductive heat transfer
Radiative heat transfer
Convective heat transfer
Phase Transition (evaporative) heat transfer

If you are talking about a hot water heater or a pot on the stove, the majority of the heating will be with direct conduction, and some convection stirring the pot. 

Light (photons) comes in many different frequencies.  Many substances may be transparent to some frequencies, and opaque to other frequencies.  So, you might have colored glass that transmits some light, but not all light.

Pure water is fairly transparent to light, but will absorb infrared and UV. 

Radiative heat isn't just limited to IR.  However, earth temperatures radiate in the IR spectrum, while the much hotter sun radiates heat in the visible spectrum.  Photons of any wavelength will generate heat when absorbed.

As far as what absorbs the photons, I think it is the electrons, but also has to do with resonance of the bonds. 

It has been years since I've done any IR spectroscopy, but you can take two similar substances such as benzene vs toluene, and they will have several of the same IR absorption peaks, but the CH3 substitution will add a few additional peaks.  Then each peak can be identified as stretching or bending of the specific covalent bond.
 

Offline jccc

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Re: How is water heated?
« Reply #2 on: 01/06/2014 02:48:42 »
Energy has many forms, but energy is force. Electromagnetic force made up mater, movement and changes in all things.

When you boiling water with fire, the fuel atoms and oxygen exchange electron bond structure and produce vibration between electron and nucleus and atoms, the vibration transfer from fire to water container, the atoms of the container start to vibrate and transfer vibration to water. Temperature is the strength of vibration.

 

Offline dlorde

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Re: How is water heated?
« Reply #3 on: 01/06/2014 11:35:40 »
Energy has many forms, but energy is force.
No. Energy isn't force. Energy (joules) is expended to apply force (newtons).
 

Online evan_au

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Re: How is water heated?
« Reply #4 on: 01/06/2014 12:30:32 »
Quote
"heat" photons (does such a beast exist?)
When you feel heat from a fire or the Sun, most of this energy is in the form of infra-red radiation (IR), which is a form of light, and does come as photons.

These photons start the water molecules in your skin vibrating more vigorously, which can be measured as an increase in temperature. This triggers heat-sensitive nerves in your skin to relay the feeling of warmth to your brain.

Quote
So what do the heat photons interact with?
The IR photons are emitted with a wide variety of frequencies, but just a limited range of frequencies will match vibration frequencies of a water molecule, and be strongly absorbed. These start the water molecules spinning, wobbling and jumping in and out (imagine a water molecule with springs between the oxygen and hydrogens - then think of every way this thing could wobble).

Quote
Why does a "heat" photon not pass through the water molecule as a light photon does?
Some frequencies are absorbed by water. Other frequencies will pass straight through, and not contribute to the warming effect.

If, however, the water is held in a blackened pot, the soot on the pot will absorb almost all IR and visible frequencies, and turn more of the incoming radiation into hot water. (On the other hand, this black surface will also be more effective at radiating this heat back into the environment, so this is a tradeoff.)

"heat" photons vs phonons
Photons will pass through a vacuum (eg from the Sun) before heating the water. This is the mechanism of heat radiation.

With a fire or an electric stove, we don't intentionally place a vacuum between the heat source and the water; in fact, vacuum is a pretty good insulator - it is one of the layers of insulation in the "thermos" flask that can hold hot and cold liquids.

With a pot on an electric stove, the electrons in the electric current run into atoms in the heating element, causing them to vibrate. These vibrations can travel through the solid element as "phonons", the quantum of sound (by analogy with photons, which are the quantum of light). These phonons can pass through the pot. When they strike the molecule of water, the phonons make the water molecule vibrate, which increases its temperature. This is the mechanism of heat conduction.

With a pot suspended above a fire, the vibrations of the hot gases released by the fire reduce the density of the air, so it rises towards the pot. This is the mechanism of heat convection. These molecules bump into the pot, transferring energy through the pot as phonons, and heating the water (as described above).
 

Offline jccc

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Re: How is water heated?
« Reply #5 on: 01/06/2014 17:24:59 »
Photon is a invented word, there is no photon but electromagnetic wave.

Space is charged, wake up.
 

Offline Bored chemist

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Re: How is water heated?
« Reply #6 on: 01/06/2014 18:09:59 »
Photon is a invented word, there is no photon but electromagnetic wave.

Space is charged, wake up.
perhaps you would like to give us a list of words that are not made up.

Also, space isn't charged- we would notice.
And how do you explain things like Compton scattering and the photoelectric effect

However, as those will all be speculation, please make any further comments in a thread in the right forum.
Don't clutter up this thread with stuff you are making up.
 

Offline jccc

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Re: How is water heated?
« Reply #7 on: 01/06/2014 18:59:43 »
Things can learn from books, can learn from thinking and watching.

They cannot explain why electrons not stick to the protons, invented a theory called what?

Photoelectric, when electromagnetic wave hits atom, if the force is strong enough, electrons will be knock out. Wave has force, no need to invent a photon to knock out electron.

If the space is not charged, matter will not form, force will not transfer. The universe is an electromagnetic field. Matter is locally condensed part of the whole field.

 

Offline jccc

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Re: How is water heated?
« Reply #8 on: 01/06/2014 20:12:34 »

[/quote]
perhaps you would like to give us a list of words that are not made up.

pa, ma, hahahahahahahaha

Also, if space is charged- we would notice.

If it is wrote in school book, we will.

The charge is leveled everywhere besides near matter, hard to noticed.
 

Offline Bored chemist

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Re: How is water heated?
« Reply #9 on: 01/06/2014 21:04:12 »
Two of those seem to be words made up by children and the last isn't exactly "made up" it's an attempt to mimic something.


Incidentally, you were also wrong about this
"Temperature is the strength of vibration."

And you are wrong about this too
"Photoelectric, when electromagnetic wave hits atom, if the force is strong enough" but I will leave it to the Mods to split this thread into your personal beliefs and the mainstream world of science before I explain why you are wrong about that.
 

Offline jccc

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Re: How is water heated?
« Reply #10 on: 01/06/2014 21:27:38 »
1972 or so, my physics pro told the whole class, that he worked with a Japanese pro to discovered a new particle, if I remembered right, k particle. The Japanese pro got a nobel prize for it. But the data to proof  the theory/math was all fake. The tested data was far from the theory predicted.

I believed him, do you? What is meanstream? Christainism?
 

Offline mxplxxx

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Re: How is water heated?
« Reply #11 on: 01/06/2014 23:38:54 »
Not a great fan of "vibration" which never gets explained to my satisfaction. How about this? The rest-mass energy of a water molecule is fixed. A water molecule can be speeded up ("heated") or slowed down ("cooled") but only as a whole entity i.e. individual atoms/electrons cannot have their speed varied. This can happen if a water molecule acts as a frame of reference as per Einstein's relativity.  A photon interacting with this frame of reference exchanges time (or power if you like, but not energy) with the frame of reference (water molecule) causing it to speed up/down. This way the photon is either cooled down (looses power) or heated up (gains power) and vice versa for the water molecule and the total energy of the system stays the same. Simple and elegant n'est pas (if you accept the premise that time is exchangeable) !?
« Last Edit: 01/06/2014 23:40:36 by mxplxxx »
 

Offline jccc

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Re: How is water heated?
« Reply #12 on: 02/06/2014 01:16:02 »
Not a great fan of "vibration" which never gets explained to my satisfaction. How about this? The rest-mass energy of a water molecule is fixed. A water molecule can be speeded up ("heated") or slowed down ("cooled") but only as a whole entity i.e. individual atoms/electrons cannot have their speed varied. This can happen if a water molecule acts as a frame of reference as per Einstein's relativity.  A photon interacting with this frame of reference exchanges time (or power if you like, but not energy) with the frame of reference (water molecule) causing it to speed up/down. This way the photon is either cooled down (looses power) or heated up (gains power) and vice versa for the water molecule and the total energy of the system stays the same. Simple and elegant n'est pas (if you accept the premise that time is exchangeable) !?
Do you believe the structure of atoms? Are electrons really constantly moving around nucleus?

Think an electron is bounded with proton by a spring to form hydrogen, then think vibration. check out this toy, it explains the neture about the spring.
« Last Edit: 12/06/2014 15:32:36 by JP »
 

Online evan_au

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Re: How is water heated?
« Reply #13 on: 02/06/2014 12:09:09 »
Quote
Not a great fan of "vibration" which never gets explained to my satisfaction.
Vibrational modes of a molecule are visible in its Infra-Red spectrum, and also affects the specific heat of gases (in the liquid phase, the specific heat of water is dominated by its electrical dipole, rather than by its geometry).

Some nice animations of atomic vibrations here: http://en.wikipedia.org/wiki/Infrared_spectroscopy#Number_of_vibrational_modes
 

Offline jccc

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Re: How is water heated?
« Reply #14 on: 02/06/2014 20:40:43 »
Quote
Not a great fan of "vibration" which never gets explained to my satisfaction.
Vibrational modes of a molecule are visible in its Infra-Red spectrum, and also affects the specific heat of gases (in the liquid phase, the specific heat of water is dominated by its electrical dipole, rather than by its geometry).

Some nice animations of atomic vibrations here: http://en.wikipedia.org/wiki/Infrared_spectroscopy#Number_of_vibrational_modes

I wish my balls are blue like those.
 

Offline mxplxxx

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Re: How is water heated?
« Reply #15 on: 03/06/2014 01:09:54 »
Quote
Not a great fan of "vibration" which never gets explained to my satisfaction.
Vibrational modes of a molecule are visible in its Infra-Red spectrum, and also affects the specific heat of gases (in the liquid phase, the specific heat of water is dominated by its electrical dipole, rather than by its geometry).

Some nice animations of atomic vibrations here: http://en.wikipedia.org/wiki/Infrared_spectroscopy#Number_of_vibrational_modes

Thanks. Being a software developer, I try and understand physics by developing simulations of the problems I study. If I can't simulate a problem it is invariably because the problem is poorly defined and/or understood in the physics community. This is an all too common event. Very few problems in physics address the "how" question. They tend to go from "what" to results via hard-to-understand mathematical equations. So it seems to be with molecular vibration. In the case of this post I am looking at finding out the low-level process by which water is heated up (e.g. the hydrogen atom absorbs a photon and it accelerates in the direction of ... etc.). I have nothing I could program a simulation on. All I am getting is high-level jargon that means nothing to me.
 

Offline jccc

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Re: How is water heated?
« Reply #16 on: 03/06/2014 02:14:44 »
Before simulate heat transfer, simulate matter structure first. Without clear understanding atomic structure, the rest is fogy.
 

Online evan_au

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Re: How is water heated?
« Reply #17 on: 12/06/2014 11:29:27 »
Another common method of heating water was not directly mentioned above: the microwave oven.

Quote from: Wikipedia
Many molecules (such as those of water) are electric dipoles, meaning that they have a partial positive charge at one end and a partial negative charge at the other, and therefore rotate as they try to align themselves with the alternating electric field of the microwaves. Rotating molecules hit other molecules and put them into motion, thus dispersing energy. This energy, when dispersed as molecular vibration in solids and liquids (i.e., as both potential energy and kinetic energy of atoms), is heat.

Microwave heating is something that could be modeled, if you want to simulate a cup of coffee at the level of individual molecules. A cup of coffee has over 1027 water molecules, which will require over 1029 bytes of memory to store the positions of all the water molecules.

It may be better to start with simulating a small sample of water containing (say) 10-100 molecules with the individual  electric charges on each oxygen & hydrogen atom, subjected to microwave radiation. Then extrapolate the temperature of this sample to the whole mass of water. This smaller simulation will easily fit into the 109 bytes of computer memory that can be economically purchased today.

But if you are interested in simulating a cup of coffee in a microwave , you can ignore the molecular-level events, and use a rough rule like "between 0.1C and 99.9C, it takes 4.2 Watts for 1 second to raise the temperature of 1 ml of water by 1C". (You need a different rule to describe what happens between -0.1C and +0.1C, or between 99.9C and 100.1C: see latent heat.)
« Last Edit: 12/06/2014 21:28:53 by evan_au »
 

Offline mxplxxx

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Re: How is water heated?
« Reply #18 on: 13/06/2014 00:41:31 »
Another common method of heating water was not directly mentioned above: the microwave oven.

Quote from: Wikipedia
Many molecules (such as those of water) are electric dipoles, meaning that they have a partial positive charge at one end and a partial negative charge at the other, and therefore rotate as they try to align themselves with the alternating electric field of the microwaves. Rotating molecules hit other molecules and put them into motion, thus dispersing energy. This energy, when dispersed as molecular vibration in solids and liquids (i.e., as both potential energy and kinetic energy of atoms), is heat.

Microwave heating is something that could be modeled, if you want to simulate a cup of coffee at the level of individual molecules. A cup of coffee has over 1027 water molecules, which will require over 1029 bytes of memory to store the positions of all the water molecules.

It may be better to start with simulating a small sample of water containing (say) 10-100 molecules with the individual  electric charges on each oxygen & hydrogen atom, subjected to microwave radiation. Then extrapolate the temperature of this sample to the whole mass of water. This smaller simulation will easily fit into the 109 bytes of computer memory that can be economically purchased today.

But if you are interested in simulating a cup of coffee in a microwave , you can ignore the molecular-level events, and use a rough rule like "between 0.1C and 99.9C, it takes 4.2 Watts for 1 second to raise the temperature of 1 ml of water by 1C". (You need a different rule to describe what happens between -0.1C and +0.1C, or between 99.9C and 100.1C: see latent heat.)
Thx Evan_au  There will likely be a certain number of molecules at which the behaviour of the system will not vary when more molecules are added. There will also likely be abstractions (high level behaviour) available to reduce the number of states in the system. If you have watched the kayak events at the Olympics you would have seen how the water flows just about the same for each competitor. A body of water being heated will have swirls and eddies that may be able to be abstracted. The thing is, there are ways and means to reduce the total number of possible states of a system and still come reasonably close to the real thing.   
« Last Edit: 13/06/2014 00:52:27 by mxplxxx »
 

Offline PmbPhy

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Re: How is water heated?
« Reply #19 on: 13/06/2014 07:32:16 »
There are many ways to heat water such as absorbing light from the sun, sum of the energy going into the kinetic energy of the water molecules and that's what hot water is, i.e. when H2O molecules have a increase in their speed and thus kinetic energy.

Place a pan of water on the stove. When the fire is in contact with the metal the kinetic energy of the gas molecules from the fire is transfered through physical contact to the metal of the pan. Then the kinetic energy of the molecules and atoms which make up the pan is transfered to the H2O molecules and that's what it means for water to become heated.
 

Offline lightarrow

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Re: How is water heated?
« Reply #20 on: 13/06/2014 11:24:22 »
Pretty basic question I know "how is water heated?" but I don't actually have an answer. Presumably via "heat" photons (does such a beast exist?).
No, it doesn't. Every "normal" photon can heat a body. If you don't believe me, point a 100mW blue-light laser on your skin for 10 second and then tell me  ;)
Quote
So what do the heat photons interact with? With the hydrogen atom, with an electron, with an oxygen atom? With a quark within one of the atoms?
Electromagnetic field interacts with every charged particle or even neutral, if it has an electric or magnetic moment. In an atom the first particles with wich EM field interact are the external electrons. If the EM wave' frequency is very high (X-Rays), it can interact with inner electrons; if it's higher (gamma-rays) it can interact with the nucleus.
Quote
Given its quantum nature, the photon cannot interact with more than one of these at once
Why? It *can* interact with more than one, if its energy is high enough. Only that the energy released to every particle with which it interacts is quantized.
Quote
. So we have (say) a hydrogen atom that has been energised via a photon. How does this affect the water molecule as a whole? What does energised mean anyway. If speeded up, how can it do so given that it is constrained by molecular forces?
It can affect the molecules in essentially 2 different ways: the first is to increase their average kinetic and potential energy while the molecules are still constrained (in this case the water's temperature increases); the second is to broke the constraint (water become liquid if it were solid or become vapour if it was liquid).
The fact water molecules can vibrate with greater average speed even if they are constrained is not difficult to understand: imagine two balls connected wit a spring. If you pull them apart of a little distance, the spring will be little stressed and when you release the balls they will start to vibrate gently, with little amplitude (maximum distance); if you pull them apart of a great distance and you release them, they will start to vibrate with a greater amplitude and so greater average distance (this greater *average* distance explains, simplistically,  thermal expansion).
Quote
What determines which atom/electron the heat photon interacts with? Why does a "heat" photon not pass through the water molecule as a light photon does? I await with interest for some replies.
The atom with which it interacts cannot be known before it does, if the EM wave extends for more than an atom's width.
A photon can "pass" or not through a water molecule, depending on the EM wave frequency: if the molecule (bond electrons, molecular dipoles, ecc.) doesn't "resonate" to that frequency, it will not absorb that photon. Actually is much more complicated than this (there is a "resonance" even in Rutherford scattering for example, but without any energy absorption from the EM field).

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Offline lightarrow

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Re: How is water heated?
« Reply #21 on: 13/06/2014 11:29:05 »
Energy has many forms, but energy is force. Electromagnetic force made up mater, movement and changes in all things.

When you boiling water with fire, the fuel atoms and oxygen exchange electron bond structure and produce vibration between electron and nucleus and atoms, the vibration transfer from fire to water container, the atoms of the container start to vibrate and transfer vibration to water. Temperature is the strength of vibration.
What I have coloured blue of your post is quite acceptable; you can forget the rest...

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Offline lightarrow

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Re: How is water heated?
« Reply #22 on: 13/06/2014 11:31:13 »
Photon is a invented word, there is no photon but electromagnetic wave.
Can you describe the "Antibunching" effect without using the photon concept?

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Offline lightarrow

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Re: How is water heated?
« Reply #23 on: 13/06/2014 11:44:31 »
...
They cannot explain why electrons not stick to the protons,
...
You are not well informed: atomic electrons *can* be found on the proton: the 1s wavefunction ψ of the hydrogen atom's electron is non-zero in the nucleus; indeed, it has its *maximum* in the nucleus!
It's the |ψ|2 multiplied the *volume element* which is zero in the nucleus, non-zero in a specific region around it (range of distances) and still zero at greater distances. This because the volum element of a spherical layer at distance "r" is 4πr2dr.

Furthermore, remember that an electron is a quantistic system, not a "little ball" orbiting around.

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Offline jccc

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Re: How is water heated?
« Reply #24 on: 17/06/2014 01:21:35 »
Electron cloud dance around nucleus, the upper shell transfer vibration to the next shell and so on, that's how heat transfer works.

What stops electron jump on proton? Is there a fence protects nucleus?
 

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Re: How is water heated?
« Reply #24 on: 17/06/2014 01:21:35 »

 

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