How do instant cold packs work? 🧐🥶 Instant cold packs work by using an endothermic reaction: you squeeze the pack to break an inner bag of water, which mixes with a solid compound like urea or ammonium nitrate. This mixing process absorbs heat from its surroundings, including the air and anything the pack touches, making it feel cold! #science #physics #technology #knowledge #howitsmade | Learning with Lyrics