Supercooled sodium thiosulfate solution

When crystals touch the liquid surface it rapidly starts freezing.

Scientific name: Sodium thiosulfate crystallizes from supercooled state.


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Reaction formula

Na2S2O3(melt) → Na2S2O3 (solid)

Step-by-step instruction

  1. To perform this experiment you should prepare sodium thiosulfate.
  2. Fill the test tube with sodium thiosulfate.
  3. Heat it in a water bath until it melts.
  4. Pour liquid into the Petri dish.
  5. Wait for it to cool.
  6. To start freezing add some crystals of sodium thiosulfate to the liquid or touch the liquid with a stick.

Scientific background

Sodium thiosulfate is a white crystalline solid at room temperature. Its melting point is 48.3 °C. When sodium thiosulfate is heated in a water bath it melts. After this it is cooled down but the substance still exists in a liquid state. This phenomenon is called supercooling. The supercooled state is very unstable. When some kind of disturbance is introduced to the system sodium thiosulfate rapidly freezes and become solid.


Published on 12 March 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst