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Let's take an example :

If I put my hand in cold water (let's say 20°C), it doesn't hurt, and it doesn't burn. But if I put my hand in hot water (let's say 90°C), it hurts and my hand can get burnt.

In both cases, I do the same action : I put my hand in water. But in the second case, my hand is burt somehow. It's definitly not the water that wounds me, so it is the "heat" in the water.

I heard that the heat is, in an atomic level, the excitation of this atom. (see What is heat and how does it affect an atom?) When I put my hand in the water, the "heat", the excitation of the atoms, is transfered from the water's atoms to my hand's atoms.

So the question is simple : how does this "heat" hurt me ? Why and how does this "atom excitation" destroy the cells in my hand ?

Thank you for your time and for yours answers.

Community
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J.F.
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  • refer to this article – Iamat8 Dec 02 '15 at 12:06
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    I'm voting to close this question as off-topic because it belongs in a biology or anatomy site. – Carl Witthoft Dec 02 '15 at 15:00
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    This is an excellent question. Why people downvote genuine questions? I don't agree with the above comment that this question belongs in biology or anatomy site. The question is about the transfer of energy from one surface to another, here human tissues and what physical properties cause pain. – Binu Jasim Oct 23 '20 at 14:10

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The water will start to transfer heat to the atoms of your hand and it will increase its temperature. Almost every process going on in your body is fine-tuned to happen in very narrow range of temperatures. Therefore if you drastically increase the temperature lots of non-standard things may happen:

  • Large molecules can rip apart due to their atoms moving too fast chaotically
  • Fluids or gases may change volume significantly, possibly ripping some tissue that holds them
  • Chemical reactions happening in your body suddenly start going on faster or stop completely
  • Completely new chemical reactions can occur completely altering the normal procesess and chemical composition. For example in higher temperatures we distinguish https://en.wikipedia.org/wiki/Maillard_reaction, that is essential to baking things.
airguru
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