Sorry if I'm asking something stupid but I'm trying to understand where this energy gets from. As far as I could find, it is not a reaction as both chemicals left unchanged, so it might have something to do with hydrogen bonding but I can't connect these two facts together.

UPD: it is not homework question (I have a degree in a completely unrelated field) and I did try to find a reasonable explanation in search engines but with no luck. Atm my theory is that ethanol creates H-bonds with water and those bonds have less energy than the ones between H2O-H2O and the excess of the energy goes away as heat but I don't have anybody who could confirm or reject that. As for the forums - Stack Exchange branches to me is the most credible source so I went asking here first.

  • $\begingroup$ There is not much to connect. Some compounds like to stay together, some don't. $\endgroup$ May 1 '19 at 0:08
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    $\begingroup$ why minus? if you see how to improve the question - let me know, otherwise your downvote is kinda pointless ;) $\endgroup$
    – skwisgaar
    May 1 '19 at 0:10
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    $\begingroup$ I don't know why minus. Guess someone doesn't like something about your question. To me, it's OK. Here, have a plus. $\endgroup$ May 1 '19 at 0:13
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    $\begingroup$ @skwisgaar, don't be discouraged by minus or pluses. These upvotes or downvotes don't mean anything in real life (may be in the virtual world). It is a good question. $\endgroup$
    – M. Farooq
    May 1 '19 at 0:29
  • $\begingroup$ I didn't downvote, but I think it's a homework question discussed in the majority of introductory chemistry books, and yes, you are right, it's about H-bonding. $\endgroup$
    – andselisk
    May 1 '19 at 2:49