[alancalverd]

Acceptance of a ball-and-spring electrostatic model of intermolecular energy exchange. 

[hamdani yusuf (OP)]

Acceptance of a ball-and-spring electrostatic model of intermolecular energy exchange. 

The model might work for solid objects. How does it work for liquid,  gas, or plasma?

[alancalverd]

Very loose springs for liquids, billiard balls for gases. Plasma temperature is a bit vague (as is the definition of plasma!) but still refers to the mean kinetic energy per particle

However, because of the large difference in mass between electrons and ions, their temperatures may be different, sometimes significantly so. This is especially common in weakly ionized technological plasmas, where the ions are often near the ambient temperature while electrons reach thousands of kelvin. The opposite case is the z-pinch plasma where the ion temperature may exceed that of electrons.

(Wikipedia).

A good friend measures the temperature of plasmas in tokamaks by studying the black body emission spectrum. 

[Spamessays]

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[hamdani yusuf (OP)]

A good friend measures the temperature of plasmas in tokamaks by studying the black body emission spectrum. 

Did the plasma produce black body radiation spectra?

[hamdani yusuf (OP)]

Very loose springs for liquids, billiard balls for gases.

Ok. So the ball and spring model only works for solid. I don't think it is useful to answer the question in the title of this thread.
 

[Bored chemist]

Ok. So the ball and spring model only works for solid.

Not really.
It works OK for liquids too. It's also useful for gases.

[alancalverd]

Very loose springs for liquids, billiard balls for gases.

Ok. So the ball and spring model only works for solid. I don't think it is useful to answer the question in the title of this thread.
 

It's ideal. Ice floats because the springs are rigid and tetrahedrally disposed, water is denser because the springs are slack and the liquid is long-range disordered. The absorption spectrum of water vapor is enormous and complicated because H2O forms all sorts of temporary polymers that work as various-sized sticky billiard balls with weak springs joining the strongly-bonded and not-very-symmetric individual molecules.

[luplay]

useful thread
I have learned a lot.

[hamdani yusuf (OP)]

useful thread
I have learned a lot.

Interesting. What have you learned?
Do you think there's a net heat exchange between water and ice at 0 degree C?

[alancalverd]

I hope not - that would destroy the whole of thermodynamics.

[hamdani yusuf (OP)]

I hope not - that would destroy the whole of thermodynamics.

Or perhaps less dramatically, your understanding of thermodynamics.
Has anyone ever actually did the experiment? What's the step by step procedure to minimize sources of errors, and get reliable result to answer the question?

[Bored chemist]

Has anyone ever actually did the experiment?

Which experiment?
Do you realise that every experiment in thermodynamics requires that the zeroth law works.
If your idea was right then no experiment would work

[alancalverd]

Let's go back to square one.
Temperature is the mean internal kinetic energy of a body.
Heat flows from a hotter body (one with a higher temperature) to a cooler one.
If the opposite were true, we could extract an infinite amount of energy  from any two bodies since the heat could flow from A to B then back to A. There is no evidence that this can happen and it would contradict our definition of energy as a conserved quantity.
Therefore we must conclude that no heat can flow between bodies at the same temperature. 

[hamdani yusuf (OP)]

Which experiment?

The experiment described in the first post.
Here's my idea to minimize noise over signal:
- Prepare 50/50 ice-water mixture at around 0°C in a large plastic bowl. Let it in refrigerator for an hour to reach equilibrium.
- Fill a metal cup with 90% water and 10% ice from the mixture.
- Fill another metal cup with 10% water and 90% ice from the mixture.
- Put both metal cups into the bowl containing the remaining of the mixture.
- Let them in refrigerator for an hour to reach equilibrium.
- See the result, if the ratio of ice-water in the cups change.

What do we expect if there is a net heat exchange?
What do we expect if there is no net heat exchange?

Do you think this experiment can provide the answer?
Is there something need to be done to avoid erroneous conclusion?

[hamdani yusuf (OP)]

Let's go back to square one.
Temperature is the mean internal kinetic energy of a body.
Heat flows from a hotter body (one with a higher temperature) to a cooler one.
If the opposite were true, we could extract an infinite amount of energy  from any two bodies since the heat could flow from A to B then back to A. There is no evidence that this can happen and it would contradict our definition of energy as a conserved quantity.
Therefore we must conclude that no heat can flow between bodies at the same temperature. 

Eternal Student has answered the question which is different than yours. Where do you think he got it wrong?

Hi.

   If I recall, there was a situation described by someone (Hamdani?) earlier.
There was a container insulated to the outside world but with a barrier between two inner regions.  The barrier allowed thermal contact between the two regions.    Region I was filled with mainly ice (and let's say some liquid water to ensure good thermal contact) at 0 deg C.     Meanwhile, Region II was filled with mainly liquid water at 0 deg C.  So everything is held at 0 deg. C on a macroscopic scale.
    If the barrier is a perfect insulator then the reasonable expectation of microscopic random interactions is that some melting and some freezing will occur in each region, it's just that overall there's no net change.   However, the barrier is a problem because it can pass energy over to the other region if a phase change occurs close to the barrier.
   There is more ice in region I so, just by the assumption of random phase shifts on a microscopic scale, melting happens more often in region I than in region II  (and conversely freezing is more frequent in region II than region I).  Over time, I would expect an equilibrium to be reached where there is an equal proportion of ice and liquid in both regions. 
   That does mean that a significant proportion of the originally liquid region has frozen while a significant amount of the icy region has melted:  There has been a net transfer of energy (latent heat) from one region to the other.
    (I've never actually done the experiment, just seems reasonable).

   Also, on a minor note:  Water changes density when freezing.  I've been ignoring pressure and volume changes. 
   
Best Wishes.

And Here's mine.

Ice melting is an endothermic process. The molecule undergoing this phase transition has local temperature lower than its surroundings where no phase transition is occurring

Like you said melting is endothermic, but there is no temperature difference so there is no bulk heat flow and hence no bulk melting.  This has been said multiple time in multiple ways, so I am not sure where your problem is.

I'd like to add that freezing is an exothermic process before I continue. In a mixture of water and ice in equilibrium, melting and freezing happen at the same rate. 
The key concepts here are fluctuation and local temperature difference. In the side where there's more ice, melting occurs more often than freezing. On the other hand, in the side where there's more water,  freezing occurs more often than melting.

[alancalverd]

Eternal Student has answered the question which is different than yours. Where do you think he got it wrong?

Quote from: Eternal Student on 22/03/2022 23:22:18
Hi.

   If I recall, there was a situation described by someone (Hamdani?) earlier.
There was a container insulated to the outside world but with a barrier between two inner regions.  The barrier allowed thermal contact between the two regions.    Region I was filled with mainly ice (and let's say some liquid water to ensure good thermal contact) at 0 deg C.     Meanwhile, Region II was filled with mainly liquid water at 0 deg C.  So everything is held at 0 deg. C on a macroscopic scale.
    If the barrier is a perfect insulator then the reasonable expectation of microscopic random interactions is that some melting and some freezing will occur in each region, it's just that overall there's no net change.   However, the barrier is a problem because it can pass energy over to the other region if a phase change occurs close to the barrier.

Alas, no. Melting and freezing require an exchange of heat because the potential energy of the two states is different. If you are in the ice block, there is no adjacent area at a higher temperature therefore no heat input. If you are in the water puddle, there is no adjacent area at a lower temperature therefore no heat loss.

[hamdani yusuf (OP)]

Alas, no. Melting and freezing require an exchange of heat because the potential energy of the two states is different. If you are in the ice block, there is no adjacent area at a higher temperature therefore no heat input. If you are in the water puddle, there is no adjacent area at a lower temperature therefore no heat loss.

What if you are at the interface between water and ice?
Or at the metal surface between ice-rich side and water-rich side?

What do you think about my planned experiment?

Here's my idea to minimize noise over signal:
- Prepare 50/50 ice-water mixture at around 0°C in a large plastic bowl. Let it in refrigerator for an hour to reach equilibrium.
- Fill a metal cup with 90% water and 10% ice from the mixture.
- Fill another metal cup with 10% water and 90% ice from the mixture.
- Put both metal cups into the bowl containing the remaining of the mixture.
- Let them in refrigerator for an hour to reach equilibrium.
- See the result, if the ratio of ice-water in the cups change.

What do we expect if there is a net heat exchange?
What do we expect if there is no net heat exchange?

Do you think this experiment can provide the answer?
Is there something need to be done to avoid erroneous conclusion?

[Bored chemist]

What if you are at the interface between water and ice?

Then there is no temperature difference to drive the transfer of energy.

See the result, if the ratio of ice-water in the cups change.

It won't.
Because, that would require the transfer of heat to or from teh ice and, because everything is at the same temperature, there is no impetus to drive the energy from one place to another.

Why do you not understand and accept this?
Which bit does not make sense to you?

[alancalverd]

What if you are at the interface between water and ice?
Or at the metal surface between ice-rich side and water-rich side?

Wherever you are in the entire universe, heat can only flow from a hot body (one at a higher temperature)  to a cold one.

BC and ES will leap on this by saying "what happens when a cold planet emits a thermal photon that travels towards the sun?" but the magic word in the OP is "net"  and the definition of temperature:  a statistic of large numbers, not the descriptor of a single event.

The problem with your experiment (I've done similar things with ice calorimeters to measure radiation dose) is the anomalous convection of water. Recorded in detail by Darwin but nowadays known as the M'pemba effect (though M'pemba could not possibly have conducted the experiment as reported), bulk water starts moving as it freezes.