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Heat is released in an exothermic reaction and heat is absorbed in an endothermic reaction.Heat is negative for an exothermic reaction and it is positive for an exothermic reaction.Work done by a system is positive and work done on the system is negative.a. The evaporatingsweatis the system. Here the sweat absorbs heat to make the phase transition from liquid water to vapor. The reaction is endothermic and theheat is positive.b. The balloon (system) does work to expand against an external pressure. As theworkis done by the system it ispositive.c. As the chemical reaction is warmed it has absorbed heat. The reaction is endothermic and theheat is positive....