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Can someone explain in simple terms why does temperature increase when mixing water with methanol? I do not have a strong background in chemistry, but I usually have to mix both liquids (sometimes also water + ethanol) (as part of my work in a biology lab) and have always wandered about the reason behind the evident increase of temperature upon mixing. I guess that the break/formation of H-bonds is involved but I haven't found a clear ("easy-to-understand") explanation in online searches.

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    $\begingroup$ Do you have any existing thoughts on this matter? It may help us explain the science if we understand where your thought process has taken you so far. $\endgroup$ – J. Ari Oct 9 '18 at 12:46
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    $\begingroup$ I do not have a strong background in chemistry, but I usually have to mix both liquids (sometimes also water + ethanol) (as part of my work in a biology lab) and have always wandered about the reason behind the evident increase of temperature upon mixing. I guess that the break/formation of H-bonds is involved but I haven't found a clear ("easy-to-understand") explanation in online searches. $\endgroup$ – Merluzo Oct 9 '18 at 13:18
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When the methanol and water are separate, they both exhibit hydrogen bonding with themselves. When the water and methanol are mixed together, some of the existing hydrogen bonding (water-water or methanol-methanol) is disturbed and now there is hydrogen bonding between water and methanol. This new hydrogen bonding pair (water-methanol) releases energy when it forms as it is more favorable than maintaining only water-water and methanol-methanol hydrogen bonding; the temperature increase you observe is the result of the released energy warming the solution.

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