Supercooled Water: Instant Freeze

Chilling

Target supercooling depth -12 °C

Cooling rate 0.6 °C/s

Nucleation

Impurity / nucleation-site density 20%

Tap / trigger strength 2

Click/tap inside the flask once it's cold to trigger nucleation. More impurities raise the odds it freezes on its own before you tap — drag to pan, scroll/pinch to zoom.

Readout

Water temp

0.0 °C

Phase

Chilling

Deepest supercool

0.0 °C

Ice formed

The real physics

Pure, undisturbed water can stay liquid well below 0 °C — a metastable "supercooled" state — because freezing needs more than a cold temperature: it needs a nucleation site (a dust speck, a scratch, a bubble) or a large enough random thermal fluctuation to start a stable ice crystal. Classical nucleation theory says the nucleation rate rises steeply with both the depth of supercooling and the density of available nucleation sites, which is why very pure, still water can be chilled far below 0 °C while impure or disturbed water freezes near 0 °C.

A tap, pour or dropped impurity supplies that missing nucleation event. Once a crystal starts, it grows outward as a real front; each gram that crystallizes releases its latent heat of fusion (334 J/g) into the remaining liquid. That heat warms the water back up, and since crystal growth speed itself increases with how far below 0 °C the liquid still is, the front runs fastest right after the trigger and self-throttles as the bulk warms — the whole mass settles at 0 °C once the energy budget balances, converting only a fraction to ice (fraction ≈ c·ΔT⁄L, where ΔT is how deep it was supercooled) rather than freezing solid instantly.

t = 0.0 s · T = 0.0 °C

drag = pan · scroll = zoom