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Are there any chemical reactions where in order to induce the reaction, you have to heat up a substance but after the reactions occurs, the substance is much colder than even before you started heating it up?

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closed as too broad by Todd Minehardt, Klaus-Dieter Warzecha, M.A.R., ron, Zhe Apr 1 '17 at 21:38

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  • $\begingroup$ Well, if you consider barium hydroxide and ammonium chloride (mixing of salts), the reaction is quite endothermic and it can absorb enough heat to freeze water around it. But you don't have to heat the reactants. It's enough if you just stir the mixture. $\endgroup$ – ShankRam Feb 13 '16 at 13:42