How does a liquid heating rod work?



Principle:

The solubility of a solute in a solvent is constant. For example, the solubility of table salt (NaCl) in water is 36g/100mL water at room temperature. When the concentration of a solution equals its solubility, the solution is called a saturated solution; when the concentration is higher than its solubility, the solution is called.





Liquid heating rod;

The most common example is a hand warmer (warm pack); the liquid inside a hand warmer issodium acetate (). When we twist the metal disc inside, the slight vibration is enough to cause the solute to crystallize, turning into a more stable solid; however, this process is exothermic, so the hand warmer begins to heat up. The hand warmer has an advantage: it can be reused. Simply place the hand warmer in boiling water for about 10 minutes, and the crystallized solute will dissolve again; this is because at high temperatures, the solubility of the solute increases. During the dissolution process, the solute undergoes an endothermic reaction, becoming.