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Supercooled Water
You will need:
- Salt
- Water (preferably bottled or distilled)
- A vessel (e.g. a plant holder)
- A thin disposable beaker, very clean
What to do:
1. Half fill a vessel with brine (as much salt as the water will hold) and put into the freezer2. After a few hours take it out and mash it up a bit - you will have brine slush at about -12 to -15C.
3. Push into the slush a thin disposable beaker containing about 2cm depth of bottled water from the fridge.
4. Leave for 20min. The water is now supercooled.
5. Take out the beaker and pour the supercooled water into an empty beaker - it freezes into a slush on impact!
Ice cannot form in the supercooled water unless there are nuclei for it to form on. In a similar way, cloud droplets do not necessarily form, even if the water vapour in the air is supercooled, if there are no condensation nuclei present.
Find out more:
Alternative experiment: http://www.stevespanglerscience.com/experiment/instant-freeze-soda-ice
Cloud condensation nuclei:
http://en.wikipedia.org/wiki/Condensation_nuclei
Cloud seeding experiments: