Sofortgefrieren: unterkühltes Wasser

Auslösung spontaner Kristallisation von unterkühltem Wasser

Classroom Demonstrations Beginner (Middle School) 120 Min. ~$3,00

Ziel

Unterkühlung demonstrieren, indem gereinigtes Wasser unter 0 °C abgekühlt wird, ohne dass es gefriert, und dann eine spontane Kristallisation ausgelöst wird.

Hintergrund

Pure water can be cooled below its freezing point (0°C) without solidifying if there are no nucleation sites for ice crystals to form. This metastable state, called supercooling, can persist down to about −40°C for very pure water. When a supercooled sample is disturbed (tapped, shaken, or a small ice crystal is added), crystallization cascades through the entire sample in seconds, creating a dramatic visual effect.

Sicherheitswarnungen

  • Handle glass thermometers with care
  • Do not use glass bottles — they may shatter if water freezes and expands
  • Supercooled water will freeze instantly if disturbed — handle very gently

Erforderliche PSA

goggles

Materialien

  • Purified water (distilled or deionized) (500 mL)
    Must be very pure
  • Clean plastic bottles (5)
    New, unopened, smooth interior
  • Small ice crystal (1)
    Nucleation seed
  • Thermometer (−20 to 10°C) (1)

Ausrüstung

Freezer (set to −8 to −10°C) Bowl Timer

Durchführung

1

Place 5 sealed bottles of purified water in the freezer, undisturbed. Set a timer for 90 minutes (adjust based on freezer temperature).

90 Min. Do not disturb the bottles
2

Very carefully remove one bottle. If it is still liquid and the temperature reads below 0°C, it is supercooled.

5 Min. Handle extremely gently
3

Method 1 (Impact nucleation): Sharply tap the bottle on a table. Watch ice crystals propagate through the liquid.

2 Min.
4

Method 2 (Seed crystal): Carefully open a second supercooled bottle and drop a small ice chip in. Watch instant freezing from the crystal seed.

3 Min.
5

Method 3 (Pour): Slowly pour supercooled water onto an ice cube in a bowl. Watch an ice tower build up.

5 Min.
6

Discuss nucleation, supercooling, and phase transitions. Explain why purity and smooth container walls are essential.

15 Min.

Erwartete Ergebnisse

The water remains liquid below 0°C until disturbed. Upon nucleation, ice crystals propagate visibly through the bottle in 2–5 seconds. Pouring onto an ice cube creates a growing column of ice.

Aufräumen

Thaw any frozen bottles. No chemical waste. Return thermometer to storage.

Details

Kategorie
Classroom Demonstrations
Schwierigkeit
Beginner (Middle School)
Dauer
120 Min.
Geschätzte Kosten
$3,00
Schritte
6
Materialien
4

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Frequently Asked Questions

What is the objective of Sofortgefrieren: unterkühltes Wasser?
Unterkühlung demonstrieren, indem gereinigtes Wasser unter 0 °C abgekühlt wird, ohne dass es gefriert, und dann eine spontane Kristallisation ausgelöst wird.
How difficult is Sofortgefrieren: unterkühltes Wasser?
This experiment is rated as Beginner (Middle School). It takes approximately 120 minutes to complete.
What safety precautions are needed for Sofortgefrieren: unterkühltes Wasser?
Key safety precautions include: Handle glass thermometers with care; Do not use glass bottles — they may shatter if water freezes and expands; Supercooled water will freeze instantly if disturbed — handle very gently.
What materials are needed for Sofortgefrieren: unterkühltes Wasser?
The main materials required are: Purified water (distilled or deionized), Clean plastic bottles, Small ice crystal, Thermometer (−20 to 10°C).
What results should I expect from Sofortgefrieren: unterkühltes Wasser?
The water remains liquid below 0°C until disturbed. Upon nucleation, ice crystals propagate visibly through the bottle in 2–5 seconds. Pouring onto an ice cube creates a growing column of ice.