Answer:
releases energy
Explanation:
In order to make a hot pack, a chemical that releases heat must be used.
A hot pack is typically a pack that is used to applied heat to injured parts of the body during physical activities to relieve pain and reduce swelling.
Hence, in order to make a chemical-based hot pack, a chemical that releases heat when in solution should be used. In order words, a chemical that elicits an exothermic reaction in solution must be used.
This is as opposed to cold packs in which a chemical that absorbs heat has to be used to generate the required coldness to treat injuries.
