Übersättigung und spontane Kristallisation

Auslösung sofortiger Kristallbildung in Natriumacetat

Crystallization Intermediate (High School) 35 Min. ~$8,00

Ziel

Eine übersättigte Natriumacetatlösung herstellen und eine schlagartige Kristallisation auslösen, um metastabile Übersättigung und exotherme Kristallisation (heißes Eis) zu demonstrieren.

Hintergrund

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.

Sicherheitswarnungen

  • 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

Erforderliche PSA

goggles

Materialien

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

Ausrüstung

250 mL beaker or flask Hot plate Stirring rod Thermometer

Durchführung

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 Min. Handle hot solution carefully
2

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

15 Min.
3

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

2 Min.
4

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

2 Min.
5

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

2 Min. Crystals will be warm
6

The process is reversible — reheat to dissolve and repeat.

5 Min.

Erwartete Ergebnisse

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.

Aufräumen

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

Details

Kategorie
Crystallization
Schwierigkeit
Intermediate (High School)
Dauer
35 Min.
Geschätzte Kosten
$8,00
Schritte
6
Materialien
2

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Frequently Asked Questions

What is the objective of Übersättigung und spontane Kristallisation?
Eine übersättigte Natriumacetatlösung herstellen und eine schlagartige Kristallisation auslösen, um metastabile Übersättigung und exotherme Kristallisation (heißes Eis) zu demonstrieren.
How difficult is Übersättigung und spontane Kristallisation?
This experiment is rated as Intermediate (High School). It takes approximately 35 minutes to complete.
What safety precautions are needed for Übersättigung und spontane Kristallisation?
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 Übersättigung und spontane Kristallisation?
The main materials required are: Sodium acetate trihydrate, Distilled water.
What results should I expect from Übersättigung und spontane Kristallisation?
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.