評論
打印
Hi, I'm Jessica
嗨，我是Jessica
and I'm gonna be talking about a chemical demonstration today that
今天我要講的化學(xué)演示
I like to call let it snow
叫作"下雪"
MIT's Dr. John Dolhun
MIT的John Dolhun博士
here he is
這就是他了
and his assistant Arielle are going to perform 2 magic tricks
他和助手Arielle將演示兩個(gè)神奇的實(shí)驗(yàn)
involving superabsorbent polymers
用到高吸水性聚合物
Let's watch as they show us the first one at the Cambridge Science Festival
首先來看劍橋科學(xué)節(jié)上他們所演示的第一個(gè)實(shí)驗(yàn)
What I'm going to do is I'm going to pour some water
我將倒一些水
into the beaker that she's holding
到她所拿的燒杯
and you keep your eyes on the beaker
你們看好燒杯里的情況
Bring it down just a bit
往下拿一點(diǎn)
Hold it for me
拿好了
Turn it to them
拿給觀眾看
We are making snow
我們在造雪
We're making snow today, Arielle
我們正在造雪 Arielle
Oh boy
乖乖
It's so cold and wet. It's just like real snow
它又冷又濕，就像真雪一樣
Look
看
So what happened?
發(fā)生了什么呢
Well, Arielle was holding a beaker containing some sodium polyacrylate
Arielle所拿的燒杯中裝有聚丙烯酸鈉
which is a polymer
這是一種聚合物
Now a polymer is a big molecule that's a chain of repeating units
聚合物是一條由重復(fù)單元組成的長鏈分子
This is the unit
這是重復(fù)單元
And this is what it looks like in a chain
這是它們組成鏈的情況
Now different chains are held together by crosslinks
不同的鏈由交聯(lián)連在一起
The etc just means that this could be thousands of carbons long etc
(等等)表示這里可以有數(shù)千個(gè)碳那么長
This is just a small part of the chain in the polymer
這只是聚合物鏈中的很小一部分
Now when water is added to the polymer
當(dāng)水被加入到聚合物中時(shí)
it wants to rush into the material
水會(huì)希望涌入到物質(zhì)中
because of the presence of so many sodium and carboxylate ions
因?yàn)檫@里有很多鈉離子和羧酸根離子
The water displaces the sodium ions
水會(huì)結(jié)合并移走鈉離子
leaving negatively charged carboxylate ions
剩下帶負(fù)電荷的羧酸根離子
