by STEM Scouts
It is better to place extra bottles in the freezer, just in case they ice over on you. Here’s how to freeze water instantly:
- Place bottles in the freezer (about two hours should work)
- Carefully remove the bottles and ensure the water is still in a liquid state
- Place the ice in your bowl
- Gently open the bottle and slowly pour water over the top
- What happens? How about if you try it with a soda?
Everyone knows that water freezes at 32°F (0°C)—or does it? When water freezes, it needs a nucleus in order for the solid crystals to form and become ice. Water is typically full of particles and impurities which have no problem kicking off the crystallization process. However, purified water by definition doesn’t have those impurities. With nothing for the water molecules to latch onto, purified water can be supercooled as far as -40°F (-40°C).
For the purposes of your at-home experiment, the water doesn’t need to be cooled that far. In just under 3 hours, the bottles of water have been chilled to -11°F (-24°C). Of course, individual settings on freezers will likely alter the time and temperature it will take to supercool the water.
The energy generated from a firm hit on the side of the bottle forces the supercooled water molecules to form a crystal in a process called nucleation. That nucleus ice crystal is all that’s needed to start a chain reaction of crystallization throughout the entire bottle. Shaking or jostling the bottle has the same effect, so be very careful and have a steady hand when removing the water from your freezer.
Pouring the water onto a bowl of ice cubes forms a slushy ice. As the supercooled water hits the ice cube nuclei in the bowl, the crystallization spreads up the stream of the water as it gets poured onto the pile. The latent heat that is released during the freezing process stops it from freezing solid. Dropping an ice cube directly down into a glass or just touching an ice cube to the surface of the water provides the nucleus needed for the supercooled water to freeze completely.
Special thanks to IFL Science for the experiment write-up.