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  • [intro]

  • I know right? That was so weird! I wonder ifOh, hi! Squeaks and I just got  

  • back from a nature walk! And we saw the strangest thing:  

  • a tree branch that looked like  it was growing white hair!  

  • We took some picturessee? It looks just like hair!  

  • We decided we wanted to investigate it further, so we carefully took a branch back to The Fort.  

  • We were going to look at it under the  microscope and maybe run some tests on it.  

  • But by the time we got back, the  hair had turned into this liquid!  

  • Anyhow, we just asked The Fort's  supercomputer to figure out what we found.  

  • And we were just waiting for the results... [Ding!]  

  • Perfect timing! Aha! What we found was actually ice!  

  • And That's why it melted! [Squeaks agrees]  

  • Apparently, this kind of ice is super rare. It only appears when conditions are just right.  

  • And it forms because of a special  property of water: it's stickiness!  

  • [Squeaks squeaks] You're right, Squeakswater doesn't  

  • feel as sticky to us as stuff like honey. But it really likes to stick to itself.  

  • If we could look at water really closely, we would  see that it's made of tiny, identical pieces.  

  • And these pieces like to stick to each otherkind of like magnets!

  • And we can actually see this.

  • Watch what happens when I add drops of  water to each other on top of this penny.

  • See how the water makes a sort of bubble shape?

  • The water is sticking to itself so strongly  that it doesn't spill over the sides!

  • Scientists don't call this stickiness, though.

  • When a liquid sticks to itself  like this, they call it cohesion!

  • If we try the same thing with  another liquid, like rubbing alcohol

  • you can see it doesn't make that dome.

  • That's because the alcohol doesn't  have the same cohesion as water does.

  • [Squeaks squeaks]

  • Ah, yes Squeaks!

  • What does cohesion have to  do with that icy hair we saw?

  • Well, it turns out cohesion is a big  part of why the ice forms that way.

  • You see, the tree branches the hair ice  was growing on have water inside them.

  • That's because, if you were to look inside a tree,

  • you would find a bunch of little tubes  that carry water and nutrients all around.

  • And some of these tubes connect  to the outside of the tree,

  • making little holes that you  can see with a microscope.

  • Now, when the branch breaks off the treethese tubes can fill up with rainwater.

  • when the air around the  branches begins to get cold,

  • the water at the very edges of  these tiny holes starts to freeze.

  • And when water starts to freeze, it gets bigger

  • because all those tiny pieces of water  

  • arrange themselves intospecial pattern called a crystal,

  • and this pattern takes up way more  space than regular, liquid water.

  • And since the ice needs room, it  moves to the outside of the branch.

  • Knowing that, what do you think happens  to the liquid water that's still  

  • in the tube as that frozen part grows?

  • [Squeaks squeaks]

  • Let's think about it this way:

  • We said that the pieces that make  up water stick to each other.

  • What would happen if a group of friends were  in a line holding hands next to a doorway...and  

  • the first friend went through the door?

  • [Squeaks answers]

  • Right! The first friend would  pull on the next person in line  

  • so that they ended up next to the door!

  • [Squeaks squeaks Yes, good job, Squeaks!

  • As the frozen water goes out into the air,  

  • the next bit of water gets pulled  right up to the edge of the hole!

  • And it gets pulled there because of cohesionThen that water freezes and goes out of the hole.

  • This keeps happening over and over again….

  • until there's a long, thin hair of ice!

  • And since they were just super thin ice strands,

  • the when we brought it inside was  more than enough to melt them.

  • [Squeaks squeaks]

  • Ooo that's a good question! What do you  think would happen if we took this water  

  • and put it outside? Would it become hairs again?

  • [Squeaks squeaks] You're right. If  

  • we froze this water again, it would  just make regular ice, not hair ice

  • since it's not in that branch anymore, so  it doesn't have those holes to grow out of.

  • [ ding-noise] Oooo look at this, Squeaks!

  • Thanks to cohesion, ice can grow into  some other pretty spectacular shapes.

  • If water freezes in holes in dirt much in the  same way it does in branches that grow hair ice,

  • you can get ice needles.

  • And if it happens through long thin cracks  in plant stems, you get frost flowers!

  • We were really lucky to see this today, Squeaks!

  • [Squeaks makes a suggestion

  • That's a great idea—I bet Mister  Brown would love to see our pictures.

  • Let's go show them to him!

  • Thanks for joining us on SciShow Kids!

  • If you want to keep learning with us here at The  Fort, don't forget to hit the Subscribe button!

  • [ outro ]

[intro]

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B1 中級 美國腔

多毛的树枝和冰的另一种奇怪,奇妙的形式(Hairy Branches and Ice’s Other Weird, Wonderful Forms)

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    joey joey 發佈於 2021 年 05 月 07 日
影片單字