how do those pocket hand-warmers (that you rub to generate heat) work?
In: Chemistry
If you mean the ones I think, they are basically two or more chemicals sat in a pouch together, and they’ll react together, but they need something to start a reaction first. It’s like firewood sitting in air; there are all of the ingredients there for a fire but they need something to kick them off.
For those hand warmers, it’s generally a little metal piece inside, that you “click” to set it off. That provides the energy/prompt to start the reaction, and then it keeps going, giving off heat until it’s done.
I’m not entirely sure if the common model uses a burst of energy or an exposure of a catalyst, but the principle remains the same. Incidentally, this is basically how batteries work too; they’re just little cells full of chemicals, and when they’re prompted to work those chemicals react, pumping out energy (in that case, through electricity more than heat) until they run out.
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