he 5. Instant cold packs use an endothermic reaction. These types of ice packs are stored at room temperature rather than needing to be physically cooled before use. When one breaks a tube inside the pack, two chemicals mix or react and absorb enough energy to produce a cooling effect. Common types include solid ammonium nitrate (NH.CI) dissolving in water. Explain why the solubility of ammonium nitrate in water is a spontaneous reaction, even though it is an endothermic reaction. Use entropy of the system and surrounding to explain this. (4 marks) water solubilit of ammonium nitrate