Cold packs are often used to prevent swelling of certain athletic injuries. The pack contains ammonium nitrate and water in separate compartments. When the pack is squeezed, the partition breaks mixing the components and forming a solution that turns very cold.

Below is the reaction:

NH₄NO₃ (s) → NH⁺⁴ (aq) + NO₃⁻ (aq)

Based on the information above, is the reaction endothermic or exothermic?

Endothermic.

Explanation:

Hello,

In this case, we should remember that exothermic reactions are those that release heat since the products have more energy than the reactants, therefore a temperature increase is exhibited. On the flip side, endothermic reactions are those that absorb heat since the products have less energy than the reactants, therefore a temperature decrease is exhibited.

In such a way, since in this case the solution turns very cold, the reaction is said to be endothermic.

Best regards.