Bye-Bye Heat - An Experimental Investigation into the Heating Principle of a Simple Heating Bag

The structural diagram and part of the instruction manual for the "Bye-Bye Heat - Heating Bag" are as follows:

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I. The heating principle of this type of heating bag is: Under a certain temperature and pressure, when the concentration of the solute in a solution exceeds the solubility of the solute at that temperature and pressure, but the solute still does not precipitate, this phenomenon is called supersaturation. The solution at this time is called a supersaturated solution. Supersaturated solutions are unstable. If the solution is vibrated or solute crystals are added to the solution, the excess solute in the solution will crystallize and precipitate, eventually transforming into a stable state. The table below shows the solubility of sodium acetate at different temperatures. Sodium acetate solution releases heat during crystallization.

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II. The experimental investigation process is as follows:

1. Calculation. Prepare 5 ml of distilled water at room temperature (approximately 20℃), then add no less than 2.32 g of sodium acetate. To ensure a good crystallization heating effect, determine that 10 g of sodium acetate should be added.

2. Weighing and Measuring. Use an electronic balance and a graduated cylinder to weigh the required amounts of the two substances.

3. Preparing a Supersaturated Solution. Pour the two substances into separate test tubes, heat until the solid dissolves completely, and then cool to form a solution.

4. Crystallization and Temperature Measurement. Add a piece of iron to the supersaturated solution to trigger crystallization, and measure the temperature immediately.