Using energy transfers from reactions

Question 1

what can exothermic reactions be used for

Answer 1

exothermic reactions can be used in hand warmers and self- heating cans
crystillisation of a supersaturated solution in used in reusable warmers

disposable ones heat the surroundings for longer though

Question 2

what can endothermic reactions be used for

Answer 2

can be used in instant cold packs for sports injuries