You are working for the company that manufactures the self-heating coffee can.
They ask you find some alternative to calcium oxide in the self-heating can, also find out whether there are any suitable subatances which can be used to make the can self-cooling. Give a short report to recommend which solid will be the best choice for the self-heating and self cooling can.
Write a short advertisment of the can, targeted at 15 year old science students, which explains the science behind the way the can works.
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I will not write the report for you but I will give you information and ideas that can be used for your assignment. Currently, the self heating can works through the hydration of calcium oxide (CaO, also called quicklime). When mixed with water, the CaO becomes a hydrate and releases heat. In terms of alternatives, really any chemical process that is exothermic (gives off heat) could be used. The trick is finding one that is safe and cost effective. The simple chemical salt potassium hydroxide (KOH) has a very high heat of solvation, meaning that when dissolved in water it gives off a large amount of heat. So having a packet of dry KOH surrounded by water that could be cracked and shaken to mix and dissolve would also do the trick very cheaply and without any serious hazards.
The self cooling can is trickier. There aren't as many endothermic (absorbing heat, thus feeling cold to the touch) chemical processes available. The dissolving of ammonium chloride (NH4Cl) in water is an endothermic process (the solution feels cold to the touch). So using it the same way that the CaO and KOH cans work above could possibly work for a self cooling can.
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