Name: 如何阻止水結冰 (How to STOP Water From Freezing)
Uploaded: 2025-08-16T18:18:42.000Z
Duration: 3 min 55 s

程度副詞

Supercooling is a phenomenon where water, or some other substance, gets colder than its freezing point without freezing. It can result in very cool demonstrations where you smack a bottle of liquid water and it freezes solid before your eyes. But water can also be supercooled in a way that makes it impossible to freeze, even by smacking it. One reason to research this kind of thing is for cryogenics, since the ice crystals are often what causes damage to cell walls. If you can keep the ice crystals from forming, you can have much better luck resuscitating your frozen space traveler.

過冷是指水或其他物質的溫度低於其冰點而不結冰的現象。它可以產生非常酷的演示效果，即你拍打一瓶液態水，它就會在你眼前結成固體。但是，水也可以過冷的方式結冰，即使拍打它也不會結冰。研究這種東西的一個原因是為了低溫，因為冰晶通常會對細胞壁造成損害。如果你能阻止冰晶的形成，你就能更幸運地救活被冰凍的太空旅行者。

第二類條件句型

The basic reason supercooling is possible in the first place is that the formation of ice crystals in water has two competing factions, the interior and the surface. The interior of ice has less energy than liquid water, so the interior wants to freeze. But the surface of ice, the boundary between the ice and the liquid water, the surface actually takes more energy to form than if it just stayed liquid, so it wants to stay liquid. Who wins? Well, volume is a multiple of the radius cubed, but surface area is only a multiple of the radius squared, which means big things tend to have proportionally large interiors, while small things tend to have proportionally large surfaces. So a really, really tiny ice crystal will have proportionally way more surface than interior, and the surface's desire to melt will win over the interior's desire to freeze. In supercooled water, any really tiny ice crystals that form melt back into liquid. Only once you get a large enough ice crystal – and the exact size depends on the temperature – only with a large enough ice crystal is the interior proportionally big enough that its desire to freeze wins out over the surface, and the crystal can grow bigger and bigger and bigger. At negative 4 degrees Celsius, the tipping point is when crystals get larger than around 20 nanometers in size, aka about 70 water molecules across. At colder temperatures, the tipping point is smaller – for example, at negative 10 degrees Celsius, you only need a crystal larger than around 10 nanometers in size, about 30 molecules across. This battle between interior and exterior is why pure water cooled below the freezing point won't necessarily freeze right away – it remains as a supercooled liquid and has to wait until a crystal forms that's bigger than the tipping point and can keep growing and freeze the whole bottle. Which can happen by waiting, or by cooling the water more so the tipping point crystal size gets smaller, or if you have other stuff like minerals or dust particles in the water that can jumpstart the ice crystal formation by being bigger than the tipping point, or if you provide a jolt of energy, like by smacking the bottle. Then a crystal can get above the tipping point size and freeze.

超冷之所以可能，首先是因為水中冰晶的形成有兩個相互競爭的派別，即內部和表面。冰的內部能量小於液態水，是以內部希望結冰。但是冰的表面，也就是冰和液態水之間的邊界，表面形成冰晶實際上比保持液態水需要更多的能量，所以它想保持液態。誰贏了？體積是半徑立方的倍數，但表面積只是半徑平方的倍數，這意味著大的東西往往有相應大的內部，而小的東西往往有相應大的表面。是以，一個非常非常小的冰晶的表面積將遠遠大於內部面積，表面的融化慾望將戰勝內部的凍結慾望。在過冷的水中，任何形成的微小冰晶都會融化成液體。只有當冰晶足夠大時（具體

情態副詞

Which is all well and good, but you can actually stop supercooled water from freezing at all.

這一切都很好，但實際上你完全可以阻止過冷的水結冰。

I made a previous video about how, since water expands when it freezes, if you try to freeze water inside a rigid container, any of it that becomes ice will expand and pressurize the container, eventually stopping the rest of the water from freezing. So if you have supercooled water inside a rigid container, there aren't just the two competing factions of interior wanting to freeze and surface wanting to melt – there's a third player, pressure. Pressure makes it harder for ice crystals to grow, so pressure, like the surface, wants ice crystals to melt. Obviously, if you have a large amount of water, a tiny amount of it freezing into ice and expanding doesn't pressurize the remaining liquid very much, so a lot of ice can form before there's enough pressure to matter. Pressure simply doesn't come into the picture until way beyond the tipping point size for runaway ice crystal formation. But if you have a tiny amount of water, the pressure can be substantially affected by the formation of even a single tiny ice crystal. For containers that are smaller than a few tenths of a micrometer in size, instead of a tipping point where once an ice crystal gets big enough it keeps growing and growing, in this case the pressure's desire to melt overwhelms the interior's desire to freeze for all crystal sizes, and all ice crystals want to melt regardless of their size. So supercooled water in a tiny, rigid bottle won't freeze no matter how hard you smack it, as long as the bottle is tiny enough. For water 1°C below zero, the bottle needs to be less than 200 nm long.

我以前錄製過一段視頻，講的是由於水在結冰時會膨脹，所以如果你試圖將硬質容器中的水結冰，其中任何結成冰的部分都會膨脹並給容器加壓，最終阻止其餘的水結冰。是以，如果在硬質容器內有過冷的水，就不只是內部想凍結和表面想融化這兩派在競爭，還有第三派，那就是壓力。壓力使冰晶更難生長，是以壓力和表面一樣，希望冰晶融化。很明顯，如果你有大量的水，少量的水凝結成冰並膨脹並不會給剩餘的液體帶來很大的壓力，所以在有足夠的壓力之前就會形成大量的冰。只有當壓力遠遠超過失控冰晶形成的臨界點時，壓力才會出現。但是，如果只有極少量的水，

For water 4°C below zero, the bottle needs to be even smaller, around 50 nm. Which maybe isn't surprising, since for water 4°C below zero, the tipping point would normally be a crystal around 20 nm in size, which would be a pretty big proportion of the container.

對於零下 4 攝氏度的水，瓶子需要更小，約 50 納米。這也許並不奇怪，因為對於零下 4 攝氏度的水來說，臨界點通常是大小約為 20 納米的晶體，這在容器中所佔比例相當大。

And if you have supercooled water in a tiny, rigid bottle, but you really need it to be ice, just remember that prohibition on freezing relies on the container being rigid. If you open the bottle so pressure can escape, then smack away.

如果你把過冷的水裝在又小又硬的瓶子裡，但你真的需要它是冰，只要記住，禁止冷凍取決於容器是否堅硬。如果你把瓶子打開，讓壓力逸出，那就砸吧。

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