What is a heat pack?
It's like a hot water bottle except instead of water there are little bits of wheat. A heat pack is also referred to as a wheat pack. It works by putting the pack in the microwave and the wheat heating up, thus the name heat pack.
Most of the heatpacks contain supersaturated solution of sodium acetate that heats up when the crystallization process is started by flexing a metal disc embedded in the liquid. Since the liquid is supersaturated (concentration of a solution beyond saturation point), flexing the notched ferrous metal disc makes the solution crystallize suddenly, thereby releasing the energy of the crystal lattice. The triggered effect of the solution will generate heat for up to 45 minutes before it…
A cold pack creates a endothermic reaction when the chemical reacts, which means that energy is taken from the surrounding, which makes the packaging cold. it is the opposite with a heat pack, an exothermic reaction is created which releases the energy into the surrounding creating the heat. Hope this helped.