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Hi, I'm Jessica
嗨，我是Jessica
Today I'm gonna talk to you about a chemical demonstration I like to call
今天我要讲的化学演示叫作
colorful indicators
多彩指示剂
Indicators show us what we normally wouldn't be able to see
指示剂/物能够指示出我们一般看不到的情况
from the canary in the coal mine
包括煤矿地中的金丝雀
to a paint that changes color with temperature
随温度改变颜色的颜料
to the acid-base indicators we'll be seeing today
以及今天我们要看的酸碱指示剂
And chemist Dr. Bassam Shakhashiri
化学家Bassam Shakhashiri博士
here he is
这就是他了
is going to be showing us the demo
他将为我们进行演示
He's the president of the American Chemical Society
他是美国化学学会主席
and performing this demo right here at MIT
演示是在MIT这里进行的
You know, what I'm going to do is an experiment
下面我要做的实验
using another form of carbon dioxide that's called dry ice
将用到另一种形式的二氧化碳，叫作干冰
Dry ice is solid carbon dioxide
干冰是固态二氧化碳
and you'll notice I'm putting what on?
看这里我戴上了什么
Putting gloves
带上手套
And I'm going to open this bucket and pick up 3 chunks of carbon dioxide
我将打开这个桶，并取出三块二氧化碳
Solid, this a solid carbon dioxide
这是固态二氧化碳
Its temperature is -78 degrees Celsius
其温度是-78摄氏度
It's very cold
非常冰冷
Dry ice changes from being solid to a gas by a process we call...
干冰从固态变为气态的过程叫作…
sublimation
升华
Sublimation is happening right now but we can't see it
升华正在发生，但我们看不到
how come we can't see it?
为什么看不到呢
Because carbon dioxide is gas. It's what?
因为二氧化碳是气体，它是怎样的
It's invisible. It has no color, so
它是无色透明的
sublimation is happening right now
升华正在发生
We can't see it
我们看不到
and I'm gonna put those three back in here
我将把这三个放回去
and ask you to focus your attention
然后让你们把注意力
on what you see between my two hands here
集中到我两手中间的这里
What do you see between my two hands?
我两手中间是什么
In order to sharpen your powers of observation
为了增强你们的观察能力
and develop the skills of reporting these observations
培养你们汇报观察结果的能力
I ask you to pretend to be the play by play radio announcer
我将要求你们假装自己是一名电台解说员
describing to someone who's not with us what's going on
为没有在场的人描述发生了什么
not a TV announcer
不是电视解说员
that person's got made because the picture tells almost everything
电视解说没什么用，毕竟从图像就能看清楚一切
So, there are how many cylinders?
这里有多少个柱形容器
And what do you see inside the cylinders?
柱形容器中能看到什么
Colored liquids. I'm listening to you on the radio
有色液体，我正在收音机前听你们讲
and what I hear you say is that there are six cylinders
我听到你们说这里有六个柱形容器
and they have in them colored liquids
其中有各色液体
Come on
继续
your brain learned a lot more information than those 2 statements, right?
你们脑海里知道的信息要远远多于这两点
So they're about this big
它们大概有这么大
you said, but I can't see you on the radio saying it's about this big, right?
但我在收音机前看不到这么大是多大
You've got to do better than this
你们要给出更好的描述
Are they one hundred millimeters in size?
它们体积是100毫升吗
Are they ten liters in size? Are there somewhere in between?
它们体积是10升吗，还是在这之间
Yes, we put a bracket on it when we estimate a science, we put a bracket on it
对，我们进行科学估计时，会进行分段
Alright, and they have, yes, colored liquids
好，确实，这里有各色液体
How do you know they're liquids?
你们怎么知道是液体的
They could be jells. How can you find out?
它们也可以是胶状物，你们怎么知道不是
We shake them up a little bit
我们可以摇一摇
because we know from experience, it's a keyword
根据经验就知道了，经验是个关键字
we learn things, our brain learns things, so we use them, right?
我们学到东西，大脑学到知识，我们使用它们
So they're liquids
这些是液体
So I'm going to take chunks of dry ice
我将取一些干冰
and put them into cylinders in a very special way
放到柱形容器内
and when I get done
完成之后
you tell me what the specialty is
你们要告诉我发生了什么
What's blowing out?
什么不断冒出来
You see any bubbles?
看到泡泡了吗
What kind of bubbles are those?
这些是什么泡泡
Well, do you wanna know what's in there?
想知道这其中是什么吗
You already know what's in there, the dry ice, I put the dry ice in there
你们已经知道其中是什么了，干冰，我加入的是干冰
What did I put the dry ice into?
我把干冰加到什么中了
Into cylinders that have colored liquids in them, right?
放到装有各色液体的柱形容器中
And I put the dry ice in every other cylinder
而且干冰被放入到每隔一个的柱形容器
I didn't put it in every cylinder, right?
而不是放到每个柱形容器中
Every other cylinder
每隔一个柱形容器
leaving one for comparison purposes, so
留一个作为对比
these are dyes that change color when the pH of the liquid changes
这些是染料，其颜色会随液体pH值变化而变化
Alright, so let's break down what's happening in these cylinders
我们来分析一下柱形容器中发生的情况
There are 6 of them
总共有六个容器
and each set is a different color
每一组的颜色都不同
because they're different acid-base indicators inside them
因为每一组都是不同的酸碱指示剂
So this set starts out blue
这一组最开始是蓝色的
This one starts out pink
这一组最开始是粉色的
And the final one is purple
最后一组则是紫色的
And every cylinder contains a few drops of sodium hydroxide
每一组柱形容器中都包含少许氢氧化钠
which is a base
这是一种碱
NaOH, sodium hydroxide NaOH
氢氧化钠
and it's a base
它是一种碱
