Self-heating can

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The source of the heat for the self-heated can is an exothermic reaction that the user initiates by pressing on the bottom of the can. The can is manufactured as three containers. A container for the beverage surrounds a container of the heating agent separated from a container of water by a thin breakable membrane. When the user pushes on the bottom of the can, a rod pierces the membrane, allowing the water and heating agent to mix. The resulting reaction releases heat thus warms the beverage surrounding it.[1]

The heating agent and responsible reaction vary from product to product. Calcium oxide is used in the following reaction:

CaO(s)+ H2O(l) → Ca(OH)2(s)

Copper sulfate and powdered zinc can also be used, but this process is less efficient:

CuSO4(s) + Zn(s) → ZnSO4(s) + Cu(s)

Anhydrous calcium chloride is often used as well. In this case, no chemical reaction occurs, instead the heat of solution is generated.

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