Answer:
Endothermic reaction
Step-by-step explanation:
A cold pack is used as a cold compress in order to numb pain caused by minor injuries. it is useful in first aid treatment of bruises, sprains, cuts and burns in addition to the application of a bandage.
A cold pack functions by absorbing heat away from the surrounding thereby decreasing the temperature and making the surface to feel cool. This is an endothermic reaction.
In an endothermic reaction, heat is absorbed from the environment and the reaction surface feels cool. Hence, an endothermic reaction is most useful in making a cold pack because the product of the endothermic reaction will feel cool to touch making it suitable to be used as a cold pack in first aid.