The Strange and Unexpected Reason Ice is Slippery |Unusual||Unforeseen||ice||slippery Der seltsame und unerwartete Grund, warum Eis rutschig ist Ο παράξενος και απροσδόκητος λόγος που ο πάγος είναι ολισθηρός The Strange and Unexpected Reason Ice is Slippery La extraña e inesperada razón por la que el hielo resbala La raison étrange et inattendue pour laquelle la glace est glissante 氷が滑りやすい奇妙で意外な理由 얼음이 미끄러운 이상하고도 예상치 못한 이유 De vreemde en onverwachte reden waarom ijs glad is A estranha e inesperada razão pela qual o gelo é escorregadio Странная и неожиданная причина скользкости льда Buzun Kaygan Olmasının Tuhaf ve Beklenmedik Nedeni Дивна і несподівана причина, чому лід слизький 冰滑的奇怪和意想不到的原因 冰滑的奇怪和意想不到的原因

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[chatter in background and ice skates scraping] background noise||ambient noise|||ice skates|gliding on ice

[bleep] censored word

Hey smart people Joe here. I'm willing to bet you're familiar with this stuff -- ice, good old frozen H2O ||||||ready to||wager||knowledgeable about|||||||solidified|water| Hola gente inteligente Joe aquí. Estoy dispuesto a apostar que estás familiarizado con estas cosas -- hielo, buen viejo H2O congelado

If you ever really stop to think about it

I mean sure we put it in our drinks, we slip on it, we slide on it, we skate on it... ||||||||beverages||slip on||||glide||||glide|| Claro que lo echamos en la bebida, nos resbalamos, nos deslizamos, patinamos...

And we're worried climate change is gonna melt every last bit of it ||concerned|||||cause to melt||||| Y nos preocupa que el cambio climático derrita hasta el último trozo

But even though ice is such a common and ordinary substance |||||||frequent and typical|||material

It still has a few weird properties and mysteries that we're just now figuring out |||||strange|characteristics||enigmas|||||discovering|

And one of those that we're just now learning the secrets to

is one of the most obvious questions about ice -- why is ice slippery?

[intro] introduction

The most intuitive explanation for ice's slipperiness is that there must be a thin layer of liquid water on the surface of the ice ||easy to understand|reason||ice|slippery quality||||||||thin layer||water||||top layer|||

This is an idea that goes back to the 1840s when the physicist Michael Faraday did this ||||||||||||scientist of physics|Faraday|||

He took two ice cubes -- when they were placed in contact for just a few seconds ||||ice cubes||||put|||||||a short time

They became one ice cube. |turned into|||solid block

Now Faraday thought that there must be a layer of liquid water between them that froze |||||||||||||||turned to ice

But I don't see a layer of liquid water, but maybe something has to create the layer of liquid water... Pero no veo una capa de agua líquida, pero tal vez algo tiene que crear la capa de agua líquida...

This is what's called a phase diagram, and this one is for water ||||||phase diagram|||||| Dit is wat een fasediagram wordt genoemd, en dit is voor water

for a particular temperature and pressure it tells you which phase -- solid, liquid or gas ||specific|||atmospheric pressure||||||solid phase|||

the substance will be in. Looking at the diagram

We see water at minus five degrees Celsius and 1 atmosphere of pressure ||||below||temperature unit|Celsius scale||||

... like your typical ice rink will be solid ice. This phase diagram also shows us something else ||||surface|||||||||illustrates||| ... como la típica pista de hielo será hielo sólido. Este diagrama de fase también nos muestra algo más

There's more than one way to melt ice

You can raise the temperature

We're all familiar with that way of melting. But water is special because you can also melt it by increasing the pressure |||||||phase change||||||||||||raising|| Todos conocemos esa forma de fundir. Pero el agua es especial porque también se puede fundir aumentando la presión

And for most substances their solid form is more dense than in the liquid form -- think of candle wax |||materials||||||||||||||candle wax|candle wax

so putting the solid form under more pressure only makes it more solid.

But water ice is different and weird

Its liquid form is more dense than the solid form

and that's why ice floats ||||sits on top

So if we take solid ice and squeeze it under a lot of pressure -- when we force it to be more dense |||||||compress|||||||||||||| Así que si tomamos hielo sólido y lo apretamos bajo mucha presión - cuando lo forzamos a ser más denso

It can become a liquid again. Even at much colder temperatures where we'd usually expect it to be a solid ||turns|||||||||||typically||||||

[ice skates scrape] ||make contact [patines de hielo raspar]

So the idea is this:

when you step onto the ice, you exert a pressure on the area under your feet that lowers the melting point of the ice and ||place your foot|||||apply||||||||||reduces|||||||

creates a thin layer of liquid forms|||||

-- slippery water. Now pressure does lower the melting point of ice. For a long time people thought that this "pressure melting"

was the reason ice was slippery -- a person's weight, concentrated on the area under their feet, melted the top layer of the ice |||||||individual's||focused|||||||caused to liquef||upper||||

But something doesn't add up here |||make sense|| Pero algo no cuadra aquí

I weigh about 88 kilograms and the area under these skates is like |weigh approximately||kg||||||||

900 square millimetres area measurement|millimeter units

-- you plug that into the appropriate equations and it turns out it only lowers the melting point of ice by a |||||correct|formulas|||results|||||||||||

fraction of one degree Celsius and if you're wearing regular shoes |||temperature unit|||||wearing regular shoes|typical|typical footwear

you'd lower the melting point by even less. Basically for pressure melting to work, you'd have to be an elephant in stiletto heels you would|||||||||||||||||||large animal||high heels|stiletto shoes bajarías el punto de fusión aún menos. Básicamente para que la fusión a presión funcione, tendrías que ser un elefante con tacones de aguja je zou het smeltpunt nog minder verlagen. Om het smelten van de druk te laten werken, moet je een olifant op naaldhakken zijn

Look at that phase diagram again. To get the kind of pressure on ice skates needed to lower the melting point of water by any |||||||||||||||required|||||||||

significant amount, I need to weigh over 3,000 kilograms |over 3000||||||

That's only half as heavy as most elephants. ||||weight|||the large mammals

There's another answer that feels closer to the truth -- friction ||||seems|nearer|||reality| Hay otra respuesta que se acerca más a la verdad: la fricción.

My ice skates are gliding across the ice ||||sliding smoothly||| Mis patines se deslizan por el hielo

They create friction. That friction creates heat and that can create a thin layer of liquid water on top of the ice

Right, we know this does happen -- ice skates gliding across ice can create friction that can melt the ice beneath them |||||occur|||sliding smoothly||||||||||||

But it also can't be the whole story

Because anyone who's tried skating for the first time knows you don't have to move very much for your feet to slip out from under you |any person|who has|attempted|ice skating||||||||||shift||||||||||| Porque cualquiera que haya probado a patinar por primera vez sabe que no hace falta moverse mucho para que se te resbalen los pies.

and it also doesn't explain why you don't have to move for ice to be slippery. So does friction explain it?

Well, maybe in part, but it doesn't explain the whole story of why ice is slippery |||||||||||||||smooth and slick

There's a fundamental issue here that we haven't talked about ||basic|problem||||have not|discussed|

Imagine a layer of water on some hard surface like a puddle on a smooth floor |||||||||||small pool||||ground surface Imagina una capa de agua sobre una superficie dura, como un charco sobre un suelo liso.

It's pretty obvious that ice is actually way more slippery than just water Es bastante obvio que el hielo es mucho más resbaladizo que el agua...

There must be something else going on. Several theoretical and experimental ||||||||conceptual||practical

In the last few years have found the real cause of ice's slipperiness -- that thin layer of liquid water on the surface>

It isn't really liquid water at all. But it's also not solid ice

It's something very different and very strange. Okay. Do you remember the weirdest property of solid water? |||||||Alright then|||||most unusual|characteristic|||

It floats

Water solid form is less dense than its liquid form. I mean think about it. That is weird solid rocks

Don't float on lava |stay on top||molten rock

But now let's think about this on the molecular level -- water is a polar molecule

The slightly positive hydrogen's are attracted to the slightly negative oxygens ||slightly positive|hydrogen atoms||drawn to||||less positive|oxygen atoms De licht positieve waterstofatomen worden aangetrokken door de licht negatieve zuurstofatomen

It's known as hydrogen bonding -- a single molecule in liquid water will only be hydrogen bonded to a few other water molecules ||||connected|||||||||||connected||||||particles Es lo que se conoce como enlace de hidrógeno: una molécula de agua líquida sólo estará unida por enlace de hidrógeno a unas pocas moléculas de agua.

But a single water molecule in ice will have more molecules hydrogen bonded to it than in liquid water Pero una sola molécula de agua en el hielo tendrá más moléculas unidas por enlaces de hidrógeno que en el agua líquida.

This makes ice a crystalline solid with water molecules bonded together basically trapped in a very consistent repeated pattern ||||solid structure||||||with each other||||||uniform||repeated arrangement

But what about a molecule on the surface of the ice?

Those may be bonded to as few as just one other Éstos pueden estar vinculados a tan sólo otro

Molecule in the crystal and it's this lack of structure that allows the surface molecules to basically tumble around in disorder |||solid state||||absence||||permits||||||move freely|move about||chaos Molécula en el cristal y es esta falta de estructura la que permite a las moléculas de la superficie básicamente dar tumbos en desorden.

Detaching and then reattaching themselves to the surface and to each other Separating|||reattaching themselves|themselves||||||| Zich losmaken en zich vervolgens weer hechten aan de oppervlakte en aan elkaar

Think about it like this:

These water molecules down here represent those deeper in the ice |||||correspond to|||||

They're held in place pretty rigidly by all the hydrogen bonds surrounding them. But up here on the surface |kept||||stably||||||around them||||||| Se mantienen en su lugar con bastante rigidez por todos los enlaces de hidrógeno que los rodean. Pero aquí en la superficie

These water molecules don't have as many hydrogen bonds holding them in place and they're able to sort of roll around |||||||||keeping|||||||||||

This creates something on the surface that isn't really a liquid because water's phase diagram says that technically speaking ||||||||||||water|||||in a technical sense|technically

Water is solid under these conditions, but it's not totally a solid either -- at least not the way that we normally think of solids |||||circumstances|||||||||||||||typically|||solid state

Scientists call it a quasi-liquid layer ||||almost liquid||

one researcher who studied its properties compared it to |scientist||examined|||||

Marbles scattered across a dance floor. You just take one step and the marbles roll out from under you small balls|spread out|||dance floor||||||||||||||

Scientists still have a lot of questions about the properties of this quasi-liquid layer

Since the border between it and ice is really hard to see ||boundary|||||||||

We're not even sure exactly how thick it is ||||precisely||depth||

All that it's somewhere between the size of a single bacterium and a thousand times smaller than that. We're talking like a few molecules ||||||||||single bacterium|||one thousand||||||||||

So ice is slippery because of a non-solid quasi-liquid layer of water on the surface. It's not caused by pressure |||slick||||not||||||||||||attributed||

It's not totally caused by friction

It's caused by the H2O molecules coming loose on the molecular level, and those H2O molecules ||||||||becoming detached||||||||| Se debe a que las moléculas de H2O se sueltan a nivel molecular, y esas moléculas de H2O

They don't act like liquid water. They act like something much weirder. ||behave|||||||||stranger

[ice skates scrape] ||make contact

I know it's strange to say here in the 21st century that we don't know everything that there is to know about something as ordinary |||||||||strange||||||||||||||| Sé que es extraño decir aquí, en el siglo XXI, que no sabemos todo lo que hay que saber sobre algo tan corriente

as frozen water, but I think this demonstrates something really fundamental about science |||||||shows|||||

-- that the more resolution they're able to gaze into the universe whether it's on the biggest or the smallest little molecular scales |||clarity||||look|||||||||||smallest molecular|||levels

Well, we'll always keep uncovering new discoveries and we'll always keep updating the things that we knew yesterday |we will|||revealing||findings|||||revising|the things|||||previously known

Even if it's in the places that we've been looking all along

Stay curious.

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[vocalising] ah-ah-aaah... making sounds|||sigh of relief [vocaliseren] ah-ah-aaah...

[vocalising] ...ah!

Hey, how's it going cool cats? |how is||||cool people

[ice skates scrape, fumbling noises] |||clumsy|fumbling sounds [patines de hielo raspan, ruidos torpes]

This intro is gonna kill me ||||overwhelm|

[ice skates scrape, fumbling noises]

[tragic music] sad|soundtrack

[indistinct] Did you get it? unclear or muffled||||