評(píng)論
打印
Hi, I'm Jessica
嗨，我是Jessica
and today I'm gonna talk about a reaction I like to call
今天我要講的化學(xué)演示叫作
"Midas' magic"
"邁達(dá)斯的魔術(shù)"
and before I get started, let's watch the reaction in action
在開(kāi)始之前，我們先來(lái)看看實(shí)際反應(yīng)
with the help of Dr. Bassam Shakhashiri
演示由Bassam Shakhashiri博士來(lái)做
and here he is
這就是他了
he's actually the president of the American Chemical Society
他是美國(guó)化學(xué)學(xué)會(huì)主席
and his motto is science is fun
他的格言是，科學(xué)很有趣
Here he is at MIT and let's see what he has to show us
他來(lái)到MIT，看他是怎么做的
Watch this. I take this clear and colorless liquid
看這個(gè)，這是一種無(wú)色透明液體
and I put some of it into beaker, about 100 milliliters
將一些倒入燒杯，大約100毫升
How do I know it's about 100 milliliters?
我怎么知道大約是100毫升
I'm reading the markers here on the beaker
我閱讀了燒杯上的刻度
and I take about 100 milliliters of a bit different clear and colorless liquid
再倒100毫升的另一種無(wú)色透明液體
but you don't know it's different, they look the same
但你們不知道它不同，因?yàn)榭雌饋?lái)是一樣的
and look at this look, look what's gonna happen now?
看這個(gè)，看看會(huì)發(fā)生什么
Isn't one of the most fascinating observations you make?
這非常迷人，不是嗎
You take 2 clear colorless liquid, you mix them together
將兩種無(wú)色透明液體混合
and you get a yellow substance that is insoluble in water
卻得到了一種不溶于水的黃色物質(zhì)
This is lead iodide
這是碘化鉛
I mixed potassium iodide solution with lead nitrate solution
我混合了碘化鉀溶液和硝酸鉛溶液
So the magician never tells you how the trick works
魔術(shù)師不會(huì)告訴你們?yōu)槭裁磿?huì)這樣
but in science we like to know what's going on
但科學(xué)中，我們會(huì)解釋發(fā)生了什么
So what is going on? Let's break it down
發(fā)生了什么呢，我來(lái)講解一下
Dr. Shakhashiri started with two clear colorless liquids
Shakhashiri博士使用了兩種無(wú)色透明液體
He had about 100 milliliters of lead nitrate
他用了大約100毫升的硝酸鉛
and that aqueous, it's in solution
這是溶于溶液的
and about 100 milliliters of potassium iodide
還有大約100毫升的碘化鉀
also aqueous
也是溶液狀態(tài)
and when he mixed those together
將兩者混合
he got a yellow precipitate
他得到了黃色沉淀
Let's color that in yellow
我用黃色來(lái)表示
A precipitate is a solid
沉淀物是一種固體
So how do we know what this yellow solid is?
我們?cè)趺粗肋@種黃色固體是什么呢
Well, this is a reaction that's called a double displacement reaction
這種反應(yīng)被叫作復(fù)分解反應(yīng)
And in this kind of reaction
這種反應(yīng)中
the cation and anion pairs switch places
陽(yáng)離子和陰離子相互交換
So what exactly does that mean?
什么意思呢
I'm gonna use some colors to help me out
我將用些色彩來(lái)描述
So we've got cations and anions in each of these compounds
這兩種化合物中都有陽(yáng)離子和陰離子
The cations have positive charge, so
陽(yáng)離子具有正電荷
in this case it's led which has a 2+ charge
這里鉛離子具有2+電荷
and nitrate, N03-
然后是硝酸根離子 NO
You need 2 of those to have a neutral compound
這需要兩個(gè)，才能得到中性化合物
Our other compound over here has potassium
這里另一種化合物擁有鉀離子
which has a +1
電荷是+1
an our anion is iodide
而陰離子是碘離子
which is -1
電荷是-1
