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Heat in the molecular/atomic scale

  1. Mar 15, 2014 #1
    what is the physical meaning -and nature- of heat in the molecular scale?
    how can molecules emit heat in forms other than EM radiation?

    i used to think of thermal energy of matter as the vibrational (kinetic) energy of the atoms/molecules that make up the matter. yesterday i was reading about combustion reactions and covalent bond formation in chemistry subforum; and it was mentioned that;in a combustion reaction; when new covalent bonds are formed; the binding energy of the bonds is emitted in the form of heat OR electromagnetic radiation. that was pretty confusing to me since i used to think of heat EMISSION in the molecular scale simply as EM radiation of energy (the binding energy of the new covalent bonds in the case of combustion reactions) that is emitted by molecules (new molecules that are formed by the new covalent bonds in the combustion reaction) and then absorbed and converted to vibrational (thermal) energy by their surroundings (other molecules/atoms). this obviously conradicts with the phrase "the binding energy of the bonds is emitted in the form of heat OR electromagnetic radiation" because this phrase implies that heat emission and EM emission of energy are two different conceptions, or, in other words, there are means of heat emission other than EM radiations, i wonder what are the other means of heat emission in the atomic/molecular scale? i cant think of the new molecules GAINING vibrational (kinetic) energy and delivering this energy to their surroundings by the mean of collisions; simply because these molecules, which where formed by the new covalent bonds, must LOSE energy, not GAIN it, upon the formations of new bonds.
    i hope you will correct me if iam getting these fundamental conceptions incorrectly or if iam missing any other fundamental conceptions or ideas.

    i also hope to get full explanation of this phenomenon from a thermodynamic point of view, this is why iam posting this thread here not in the chemistry subforum.
    Last edited: Mar 15, 2014
  2. jcsd
  3. Mar 15, 2014 #2

    Simon Bridge

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    Individual articles do not have "heat" - heat is a bulk property that describes the energy stored as random motions of the particles. These motions need not be vibrational - though vibrational motion is important.

    ... the binding energy is released, usually, as photons ... these photons interact with the surrounding material - heating it up.

    When the author says the energy is released as heat - they mean that the overall substance gets warmer.
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