What Causes an Instant Ice-Pack to Cool

Most first-aid kits contain instant cold compresses to treat injuries and burns. A simple chemical reaction, initiated by the user, provides for the immediate application of a cooling remedy. 

To provide cold therapy for cuts, bruises, sprains, and lacerations, an instant ice pack for first-aid treatment uses a chemical reaction that requires heat in order to occur. An instant Ice-Pack contains two compartments — one containing liquid water, the other a solid. The pack is activated by squeezing the liquid compartment to break an inner seal that permits the mixing of the two compartments. Heat is withdrawn from the surroundings by the reacting chemicals, lowering the temperature of the ice-pack contents. 

An instant ice pack for first-aid treatment uses the endothermic nature of the dissolution of an ionic salt in water to provide cold therapy. Two typical materials that absorb heat as they dissolve in water are ammonium nitrate and ammonium chloride  

The standard enthalpy of reaction for the dissolution of ammonium nitrate in water can be calculated using the enthalpies of formation for reactants and products  

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Question 10.5 What Causes an Instant Ice-Pack to Cool ... 

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