过饱和与瞬间结晶

触发醋酸钠的瞬间晶体形成

Crystallization Intermediate (High School) 35 分钟 ~$8.00

目标

配制过饱和醋酸钠溶液并触发瞬间结晶，演示亚稳过饱和和放热结晶（热冰）。

背景

Sodium acetate trihydrate can form extremely supersaturated solutions that remain liquid until disturbed. Adding a single seed crystal or scratching the container wall triggers rapid crystallization throughout the solution, releasing heat (exothermic). The resulting solid resembles ice but is warm to the touch.

安全警告

  • The solution gets hot when it crystallizes — handle with care
  • Sodium acetate is generally safe but avoid ingestion
  • Use heat-resistant gloves when handling hot solution

所需PPE

goggles

材料

  • Sodium acetate trihydrate (100 g)
    Or make from vinegar + baking soda
  • Distilled water (10 mL)
    Minimal amount

设备

250 mL beaker or flask Hot plate Stirring rod Thermometer

步骤

1

Add 100 g sodium acetate trihydrate and 10 mL water to the beaker. Heat while stirring until all crystals dissolve (about 70°C).

8 分钟 Handle hot solution carefully
2

Remove from heat and allow to cool to room temperature undisturbed. Do not shake or add anything.

15 分钟
3

Once cooled, the solution should remain liquid despite being supersaturated. Measure the temperature.

2 分钟
4

Drop a single small crystal of sodium acetate into the solution and observe the rapid crystallization wave.

2 分钟
5

Immediately measure the temperature of the newly formed crystals. Note the temperature increase (exothermic).

2 分钟 Crystals will be warm
6

The process is reversible — reheat to dissolve and repeat.

5 分钟

预期结果

When triggered, crystallization should sweep through the solution in seconds, forming a solid mass of warm crystals (hence "hot ice"). The temperature typically rises 10-20°C above room temperature. This is the principle behind reusable hand warmers.

清理

Sodium acetate is reusable. Simply reheat to dissolve. Can be disposed down the drain. Rinse equipment.

详情

类别
Crystallization
难度
Intermediate (High School)
时长
35 分钟
预估费用
$8.00
步骤数
6
材料
2

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Frequently Asked Questions

What is the objective of 过饱和与瞬间结晶?
配制过饱和醋酸钠溶液并触发瞬间结晶，演示亚稳过饱和和放热结晶（热冰）。
How difficult is 过饱和与瞬间结晶?
This experiment is rated as Intermediate (High School). It takes approximately 35 minutes to complete.
What safety precautions are needed for 过饱和与瞬间结晶?
Key safety precautions include: The solution gets hot when it crystallizes — handle with care; Sodium acetate is generally safe but avoid ingestion; Use heat-resistant gloves when handling hot solution.
What materials are needed for 过饱和与瞬间结晶?
The main materials required are: Sodium acetate trihydrate, Distilled water.
What results should I expect from 过饱和与瞬间结晶?
When triggered, crystallization should sweep through the solution in seconds, forming a solid mass of warm crystals (hence "hot ice"). The temperature typically rises 10-20°C above room temperature. This is the principle behind reusable hand warmers.