Answer:Hot and cold packs use a chemical reaction, known as an exothermic or endothermic reaction, to produce a change in temperature. Exothermic reactions release energy in the form of heat while endothermic reactions absorb heat. Hot and cold packs contain chemicals such as ammonium nitrate, sodium acetate and calcium chloride which are activated by the user by either pressing, shaking or adding water. Once activated, the chemicals react exothermically or endothermically to produce either a hot or a cold sensation.
The chemical reaction in hot/cold packs typically occurs between an acid and a base. When the acid and base are combined, they react to form a salt and water. The salt releases or absorbs heat and causes the pack to heat up or cool down. The process of releasing heat is called exothermic while the process of absorbing heat is known as endothermic.
Hot/cold packs are a great and affordable way to relieve pain and reduce swelling. They are convenient, reusable and are available in various sizes, shapes, and temperatures.
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