Final answer:
An instant cold pack is an example of an endothermic reaction. When a tube inside the pack is broken, it releases a chemical that reacts with water and absorbs heat energy.
Step-by-step explanation:
An instant cold pack is an example of an endothermic reaction. When a tube inside the pack is broken, it releases a chemical that reacts with water and absorbs heat energy. This absorption of heat energy causes the pack to quickly cool down.