Final answer:
Supercooling magnesium nitrate hexahydrate or aluminium ammonium sulfate dodecahydrate may require specific conditions to prevent crystallization. Mixing different salt hydrates for hand warmers could be explored experimentally. Hand warmers rely on the exothermic crystallization of supersaturated sodium acetate solutions to release heat.
Step-by-step explanation:
The ability to supercool a substance like magnesium nitrate hexahydrate or aluminium ammonium sulfate dodecahydrate is indeed a complex process that may be affected by factors such as purity of the substance, presence of impurities, and specific conditions under which supercooling is attempted.
As such, achieving supercooling without crystallization can be challenging. Regarding the mixing of salt hydrates, like sodium acetate trihydrate and magnesium nitrate hexahydrate, this could be possible in theory, but it would require careful experimentation to ensure that the desired endothermic or exothermic reaction occurs, and that the mixture does not prematurely crystallize.
Hand warmers function based on the exothermic recrystallization of a supersaturated solution, typically using sodium acetate. When the solution crystallizes, it releases heat which is then used to warm the hands. Commercial hand warmers exploit this process, and you can often find them in drugstores or sporting goods stores. They usually consist of a pouch containing a supersaturated solution of sodium acetate and a small metal disk. When the disk is clicked, it initiates a mechanical shockwave that triggers precipitation of the solute, which subsequently releases heat.
For your chemistry project, it might be helpful to look into the principles of thermochemistry and colligative properties, especially as they apply to solutions and supersaturated states, to better understand the mechanisms at work in the hand warmers you are studying and exploring.