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Suppose that I heat up a pot of cold water, the flame heats up the pot and conducts heat into the water. As a result, the overall average kinetic energy of the water molecules increases until water boils.

My question is about what is the atomic/molecular interaction between the hot pot and the water molecules. The atoms of pot are bound (the heat transfer will not exceed the work function of the metal) where as water molecules are unbound. From the atomic/microscopic level, how are the pot molecules increasing the kinetic energy of the water molecules? If possible, I would like to see both a classical as well as quantum mechanical explanation to this question.

I looked at Wikipedia's thermal conductivity as well as here and other posts, however, none of these address this particular question. Any help is much appreciated.

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what is the atomic/molecular interaction between the hot pot and the water molecules.

Molecules and atoms belong to the quantum mechanical framework.

The molecules and atoms in the solid of the pot are vibrating and rotating and these variations at the lattice level results in infrared radiation, the more heat the more radiation. The charge distributions in a solid are not uniform and thus motions in the field between the molecules results in radiation.

The photons from this radiation excite the rotational and vibrational levels of the water in the pot and in addition transfer momentum and kinetic energy to the water molecules.

The consequent de-excitation of the molecules in turn will also transfer momentum and energy to the water molecules, thus raising the average kinetic energy of the molecules and hence the temperature.

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  • $\begingroup$ Thank you for your answer but I still do not see how this IR radiation is being produced. If I read you correctly, heat transfer via conduction are these vibrations of the lattice. Assuming the pot is electrically neutral, how can IR radiation be produced since I assume classically that an electric charge has to be accelerated to produce EM radiation. $\endgroup$ – Los Jan 6 '17 at 21:19
  • $\begingroup$ It is not via conduction , or you could say conduction is short range radiation. Radiation occurs because even though the lattice is neutral, there are spill over fields because the atomic and molecular orbitals have "shape" which leaves regions of positive and negative electric fields. Vibrating molecules in each other's fields will radiate infrared, and in conductors where the electrons are in bands and can change energy levels continuously, they will be excited by energy coming from the energy source and de-excited releasing a photon again in the infrared. An infrared photon penetrates $\endgroup$ – anna v Jan 7 '17 at 5:12
  • $\begingroup$ the bulk water until it meets a target to excite and transfer the energy $\endgroup$ – anna v Jan 7 '17 at 5:14
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Even though the atoms are bond to the metal pot the electrons become more and more energies and pass their energy to the water by conduction (direct contact) and radiation (photons).

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  • $\begingroup$ please see my comment to anna v. $\endgroup$ – Los Jan 6 '17 at 21:17
  • $\begingroup$ The electrons are excited from the heat and then emit photons in the form of blackbody radiation. Directly proportionate to the temperature. $\endgroup$ – Bill Alsept Jan 6 '17 at 21:35
  • $\begingroup$ If I read the link provided from anna v correctly, they are lattice vibrations that produce the IR waves. So is it this IR radiation that primarily heats up the water in a hot pot? $\endgroup$ – Los Jan 6 '17 at 22:22
  • $\begingroup$ Both infrared and conduction. $\endgroup$ – Bill Alsept Jan 6 '17 at 22:26
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I am giving Classical Mechanics based on the following explanation: When you heat up a pot, which is solid and constituents are strictly bound to vibratory motion only therefore, when the constituents absorb energy they vibrate, dissipate energy and hence heat up the pot. Molecules of water gets heated due to Conduction. Being triatomic, molecules of water can translate, rotate and vibrate therefore, these motions dissipate heat.

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