Name: 水の凍結を止める方法 (How to STOP Water From Freezing)
Uploaded: 2025-08-16T18:18:42.000Z
Duration: 3 min 55 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

程度の副詞

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.

過冷却とは、水やその他の物質が、凍ることなく氷点よりも冷たくなる現象である。水の入ったボトルを叩くと、目の前でその水が固まるような、とてもクールなデモンストレーションができる。しかし、水は叩いても凍らないように過冷却することもできる。このようなことを研究する理由のひとつは、細胞壁にダメージを与える氷の結晶がしばしば発生するため、極低温研究のためである。もし氷の結晶ができないようにすることができれば、凍った宇宙旅行者を蘇生させることができる。

仮定法過去

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.

そもそも過冷却が可能な基本的な理由は、水中で氷の結晶が形成される際に、内部と表面という2つの派閥が競合するからである。氷の内部は液体の水よりもエネルギーが小さいので、内部は凍ろうとする。しかし、氷の表面（氷と液体の水の境界）は、液体のままよりも形成に多くのエネルギーを必要とするため、液体のままでありたい。どちらが勝つか？体積は半径の3乗の倍数だが、表面積は半径の2乗の倍数でしかない。つまり、大きいものは内部が比例して大きくなり、小さいものは表面が比例して大きくなる傾向がある。つまり、大きなものはそれに比例

様態の副詞

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

しかし、過冷却水が凍るのを止めることはできる。

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.

水は凍ると膨張するため、硬い容器の中で水を凍らせようとすると、氷になった水は膨張して容器を圧迫し、最終的に残りの水の凍結を止めてしまうという話を以前ビデオで紹介した。つまり、硬い容器の中に過冷却水がある場合、内部は凍りたい、表面は溶けたいという2つの派閥が競合するだけでなく、圧力という第3のプレーヤーが存在する。圧力は氷の結晶を成長させにくくするので、圧力は表面と同様に氷の結晶を溶かそうとする。明らかに、大量の水がある場合、氷に凍って膨張するわずかな水の量では、残りの液体にあまり圧力がかからないので、十分

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.

氷点下4℃の水の場合、ボトルはさらに小さくする必要があり、約50nmとなる。氷点下4℃の水の場合、ティッピングポイントは通常20nm前後の結晶であり、容器のかなり大きな割合を占めることになるからだ。

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.

また、小さな硬いボトルに過冷却水を入れていて、どうしても氷にしたい場合、凍結の禁止は容器が硬いことに依存していることを覚えておいてほしい。もしボトルを開けて圧力が逃げたら、その時は叩いてしまえ。

This video is entirely supported by patrons on Patreon. If you're already supporting, thank you so much, and if you're not, please consider it at patreon.com slash minutephysics.

このビデオはすべてPatreonのパトロンによって支えられています。すでにご支援いただいている方は、本当にありがとうございます。まだご支援いただいていない方は、patreon.com slash minutephysicsでご検討ください。