When a large amount of sodium acetate is dissolved in water, it reaches a supersaturated state (at this time, the amount of sodium acetate dissolved in water is greater than the solubility of sodium acetate at this temperature), thus releasing heat. A small amount of water is wrapped in the organic matter (paraffin) in the hand warmer, so that the water is separated from the anhydrous sodium acetate solid. When in use, the hand warmer is kneaded to break the organic matter that plays the role of wrapping, and water is combined with sodium acetate to warm hands by using the heat generated by the supersaturated solution formed by sodium acetate in water.

Matters needing attention in making hand warmers:

1, sodium acetate has high solubility in water, so it should be calculated in detail before doing the experiment to avoid drug waste.

2. Because it is necessary to achieve supersaturation to achieve the purpose of heat release, the amount of sodium acetate added in the experiment is slightly larger than the calculated amount.

3. After the hand warmer releases heat, it can be re-saturated by heating and continue to release heat.