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  • The question, "'is water wet?" may seem like it has an obvious answer, but the science

  • of it isn't that simple.

  • Water is actually really weirdlike, way weirder than you probably realizeand our

  • understanding of it may only just be coming to a boil.

  • Water... may not actually be just water at all.

  • It has at least sixty-six properties that make it really different from most other liquids.

  • Like, water has a higher surface tension than almost any other liquid.

  • More solids dissolve in water than any other substance.

  • And water is almost the only liquid in the universe where the solid form is less dense

  • that the liquid form; that's why ice floats.

  • All of water's weirdness has made life on Earth possible, and its extraordinary characteristics

  • come down to one simple bond:

  • the hydrogen bond.

  • We all know water consists of one oxygen atom bonded to two hydrogen atoms.

  • Because of the way the shared electrons side with the larger, more electronegative

  • oxygen atomwater becomes a polar moleculethe oxygen end is negative, while the hydrogen

  • end is positive.

  • And this is essential.

  • Water's polarity dictates how it interacts with absolutely everything, including all of the

  • cellular machinery that drives life.

  • But perhaps most importantly, also determines how water interacts with itself.

  • See, when you have two water molecules next to each other, their opposite ends attract,

  • just like magnets.

  • The bond that forms between water molecules is called a hydrogen bond, and it's relatively

  • weak, but it's what keeps water water.

  • At ambient conditions on Earth's surface, water should actually be a gas.

  • Instead, the hydrogen bonds between the molecules make water sticky, keeping it in liquid form.

  • And something super wild happens when you take water down to really low temperatures.

  • If it's pure water, there won't be anything to seed ice crystals, so it won't actually

  • freeze into a solid.

  • Instead it becomes supercooled water.

  • At a certain point in supercooling, research has let us see water as two different kinds of

  • liquids.

  • This is experimental evidence of something called the "two-state model" of liquid water.

  • This is mind-blowing, I know, but try to picture all of those polar molecules in a glass of

  • water.

  • Their hydrogen bonds orient them toward each other in a specific way.

  • But some molecules will get left out of those more orderly, lower density groups and are

  • forced to just cram together in a way that messes with their hydrogen bonds

  • in higher density groups.

  • A researcher in the field has a great way of describing this when he says:

  • water is not a complicated

  • liquid, but two simple liquids with a complicated relationship."

  • The two-state model of liquid water is something we've been able to model with computers

  • for decades, but it was extraordinarily difficult to observe until Anders Nilsson and his team

  • were able to get a closer look in 2017.

  • The team injected micrometer-scale water droplets into a vacuum to get them super cold super

  • fast, and then used an x-ray laser pulse to probe the water's molecular structure.

  • The laser pulses were only quadrillionths of a second long, so the team could capture

  • multiple frames, so to speak, and see how the structure between molecules changed over

  • time.

  • Like, you know, over the course of a microsecond.Their groundbreaking results provided evidence for

  • the point at which water starts to behave more like one form than the other, called

  • the "Widom line."

  • This doesn't mean water acts like this all the time, but this experimental observation

  • of these two phases of water at super cooling may provide explanations for many of water's

  • quirks, and could help us better understand important phenomena like the melting of sea

  • ice, or how to best desalinate water.

  • And it's important to remember that the two-state model of liquid water is still not widely

  • accepted; some in the field are skeptical about these observations and say that for

  • many reasons it just doesn't make sense.

  • But Nilsson and his team are continuing to explore the behavior of water at even lower

  • temperatures with even more exciting lasers, because while water still may be the most

  • abundant liquid on Earth, it's definitely the most bizarre.

  • If you want more on wild states of matter, check out this video over here, and make sure

  • you keep coming back to Seeker to learn all kinds of surprising things you never knew

  • about the world around us.

  • If you want more on the latest breaking ice research, let us know down in the comments

  • down below and as always, thanks so much for watching.

  • I'll see you next time.

The question, "'is water wet?" may seem like it has an obvious answer, but the science

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B1 water hydrogen liquid liquid water bond model

We Still Don’t Understand What Water Is, Here’s Why

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    Summer posted on 2020/09/08
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