[IDK_Melaphystos]

Ok, assume you have two components that, when mixed, create and endothermic reaction (like Ammonium Nitrate and Water). Now answer these questions:

(1) After the mixture has absorbed all the heat, what exactly remains? Something like Nitrous Oxide or whatnot (for this example)?

(2) What would one have to do to get the fundamental products back; or rather, what would one have to do to make the substance absorb more heat (recycle the reaction)?

These questions aren't just limited to Ammonium Nitrate and Water, but all endothermic counterparts.

Thanks in advance