How Do Hot & Cold Packs Work?
Hot packs are used for treating injuries and for warming hands and feet during cold weather. Heat packs promote the increase of blood to damaged areas and cold packs decrease the flow. Cold packs are also used in injuries for shrinking bruises and also for chilling food and liquids. Hot packs are composed of magnesium sulfate or calcium chloride. Cold packs are full of ammonium nitrate. Both packs have a section of water separated from the chemicals. They normally maintain their temperatures for approximately 30 minutes. When a cold pack is crushed, the thin plastic layer separating the chemicals from the water is breached. The chemicals and the water mix together, with the ammonium nitrate producing an endothermic reaction. Endothermic reactions involve the absorption of heat. The ammonium nitrate mixing with the water creates cold. The temperature of cold packs can reach a low of 32 degrees F. When a hot pack is crushed, the plastic layer keeping the water away from the chemicals is
