Brady thought that tin was a really boring element,
Brady曾认为锡是一种十分无趣的元素
but we’ve changed his mind,
但我们已经改变了他的想法
showing him that it does more than it says on the tin.
向他证明了锡还是挺有趣的
What we’re gonna show you is
我们将会向你演示
how tin melts,
锡是如何融化的
how you can join wires on the battlefield
当你在战场上被敌人射击的同时
while you’re being fired at by the enemy,
该如何焊接电线
how you can stop things growing on the bottom of ships.
你如何阻止船底附着生物的生长
And also, give you a few hints about our first-year chemistry course
同时 如果你来这所大学上学的话
if you come here to the university.
也会给你一些有关一年级化学课的建议
Tin is in group 14,
锡位于元素周期表第IVA族
the same group as carbon,
与碳元素同族
so it is below germanium and above lead.
位于锗之下 铅之上
It was really valuable in prehistoric times,
锡在史前时期相当珍贵
because it was found that when you mix it with copper,
因为人们发现当锡铜共熔
you could make bronze,
就可以制备青铜
and bronze melts at a lower temperature than copper,
因为青铜熔点低于铜
so it’s easier to make weapons,
所以更易于制造武器
and the weapons were harder.
且武器质地更为坚硬
Opener for tin?
锡的开创者?
Tin is found in a variety of minerals.
锡存在于各种矿产
There are large sources of it in China,
中国 马来西亚 还有英国西部的康沃尔
in Malaysia, and also in Cornwall in the west of England.
都有着丰富的锡矿资源
After the ore has been crushed and washed,
将含锡矿石粉碎清洗之后
the tin oxide is dried and samples tested for quality.
烘干氧化锡 测试样本的品质
A good sample should yield 140 pounds of tin from a ton of ore.
如果是优质的样品 一吨锡矿能制备出140磅的锡
There are still many abandoned tin mines in Cornwall.
康沃尔至今还有许多废弃的锡矿
They’re quite dangerous when you walk across the moors.
当你穿越荒野时 它们相当危险
There are open shafts which if you’re not looking where you’re going,
这里有开放式的竖井 倘若你不注意看脚下的路
you can fall down.
你就能跌下去
Eventually, Cornwall could provide a third of all the tin required by this country.
最终 康沃尔能提供全国总需锡量的1/3
We have been trying to look at tin, beginning with the metal.
我们一直在努力研究锡元素 最先开始研究的就是金属锡
One of the interesting things about tin is that
锡有趣的一点在于
it melts at quite a low temperature.
它的熔点很低
So if you heat it up,
如果你加热它
it melts around 230 degrees centigrade.
它在230℃左右融化
So even with a gas torch,
因此即使用气焊枪
you can melt it quite easily in the glass test tube.
你也可以很轻易地在玻璃试管中熔化它
This low melting point is very useful
锡的低熔点非常有用
for a whole series of applications,
可应用于许多方面
particularly for so-called solder,
特别是在所谓的焊接上
that is joining things electrically.
所谓焊接 就是用电将两边连在一起
This is solder.
这是焊枪
It is the metal which is used to make electrical connections,
而锡就是用于焊接的金属
in this case, on a very old computer memory board.
这里用老式电脑内存板举例
Now, to make joints like this,
做出这样的焊点
requires precise tools and it’s a bit boring.
需要精密的仪器 而且做的过程也有点无聊
But what we want to show you is
但我们想为你演示的是
how people joined wires together on the battlefield,
战士们在战场上是如何连接电线的
for example, in the Second World War.
比如 在第二次世界大战中
You’ve got to imagine,
想象一下
you’re on the battlefield, people are shooting at you.
你在战场上 敌人拿枪射击你
You need to put down the telephone wires,
你需要接通电话线
so you can talk to the groups on either side of you,
来和两边的队伍沟通
and the last thing you want to do is to get out to soldering iron,
你最后要做的就是拿出烙铁
and wait for it to heat up and so on.
然后等它升温 等等
I remembered that I had some self-soldering joints,
我记得我有一些自焊接头
which I got when I was an army cadet
是我当军校生的时候得到的
when I was about 15.
那时我才15岁
There’s a copper tube with some solder inside and some material that burns.
这是一根铜管 里面有一些焊料和易燃物
So that you can light it like a match.
所以你就可以像点燃火柴一样点燃它
So you take the two bits of electrical wire you want to join,
那么你就要准备好两条要焊接电线
post one piece of wire in each end,
在两段各插入一段电线
and then you light it.
然后点燃它
The solder is inside.
这里面就是焊料
I’ve had these 56 years,
它们在我手上56年了
and they weren’t new when I got them.
拿到它们的时候都不是新的
So they probably come from the Second World War.
所以它们很可能是第二次世界大战
They’re probably surplus.
剩下来的
I thought they would work.
我觉得它们还可以用
Neil was a bit dubious.
Neil却将信将疑
As usual, I was right.
像往常一样 我是对的
So Neil set fire to the red part,
Neil点燃了红色部分
which is some sort of igniting mixture,
它应该是某种引燃混合物
and it flared up quite quickly,
点燃后很快就出现了火光
and then you can see the whole tube gets very hot.
接着就观察到 整个铜管变得滚烫
Now, of course, you can’t see the solder because that’s inside.
但我们看不到焊料 因为它是在里面的
Then as it gets hot, the solder melts,
但随着温度升高 焊料融化
and runs around the wires.
它就会沿线流淌
And then as it cools down, it solidifies,
然后当它冷却下来 就会凝固
fixing the wires into the short piece of copper tube.
就会把电线焊接在短铜管上
On one occasion, we did it more than once,
曾经 我们做了不止一次的实验
you could see the solder coming out just on one side.
你可以看到焊料只从一端流出
Just to show that the solder was in there,
单纯地为了证明里面有焊料
I persuaded Neil and our new assistant Connor,
我说服了Neil和刚加入我们队伍的
who’s joining our team,
新助手Connor
to heat one of these pieces vertically,
对其中一个垂直加热
so that when the solder melts, it will drop out to the bottom.
这样焊料一融化 就会滴落在底部
Just to show you that it got hot,
这样你就能看出它的热量
we put the thermocouple which measures temperature into the top.
我们还在顶部放置了测温用的热电偶
So you can see the temperature going up,
因此你就可以看到温度升高
and you can see the solder running out.
还能看到焊料滴落
So we were really quite excited,
所以我们特别兴奋
then we thought tin is in the same group as carbon,
然后我们想到锡与碳同族
carbon burns, so perhaps tin will burn well in a Bunsen.
碳可燃 那么锡用本生灯加热时或许也具有良好的可燃性
We found some very nice, finely-powdered tin,
我们找来了一些精细的粉末状锡
Neil started sprinkling the tin into the flame of the Bunsen burner,
Neil开始往本生灯的火焰里撒锡
and it was really beautiful.
锡燃烧起来非常漂亮
You could see all sorts of swirling flames.
你能看到各种漩涡形的火焰
And when the tin went into the flame,
当锡被点燃后
you got quite a bright coloured light.
还能看到有色火焰
Now there’s some argument whether it was violet or lilac,
至于火焰是蓝紫色还是淡紫色 目前还存在争议
and that there was a touch of green as well, which I think came off his spatula.
此外还有一抹绿色 我认为它来自于Neil装锡粉的药匙
It was really much more beautiful than any of us had expected.
实验现象比我们任何一个人想象的都要美
And then Neil had a really good idea,
之后Neil出了个好点子
he fed the powder into the air hole of the Bunsen burner,
他将锡粉注入本生灯的气孔里
the stream of gas then blew the powder up into the flame,
气流就把锡粉吹到了火焰中
and that looked even better.
这样火焰就更好看了
So we had two really good experiments, demonstrations,
那么我们已经完成了两次特别炫酷的实验示范
and so we felt really ready to go for a third.
所以我们觉得是时候做第三个了
Now tin is very well-known of having two different forms of the metal.
众所周知 锡有两种形态
One of them is shiny and looks just like any other metal,
一种闪闪发光 就像别的金属一样
the other one is meant to be a sort of brownish color and crumbles away.
另一种是灰褐色粉末状的
This transition between the two happens at low temperature,
低温条件下 这两种形态可以相互转化
and I’d seen the terrific time-lapse video on YouTube,
我在YouTube上看到过一个很棒的延时视频
where you can see a block of metallic tin gradually crumbling away
视频中一块金属锡逐渐碎裂成粉末
as this so-called tin pest spreads across.
而这就是所谓的“锡疫”蔓延
So we thought we will try the same,
所以我们觉得可以尝试同样的实验
but perhaps we were not quite so patient.
但也许我们会比较缺乏耐心
So, first of all, I had the dice tin soldier
所以首先 我找来了小块的锡兵
and we tried dunking the soldier in liquid nitrogen.
然后我们试着锡兵浸泡在液氮里
He came out looking much the same,
它取出来后看起来基本没变化
but we hoped it had transformed inside.
但我们希望它在内部有所变化
So Neil thumped it with a hammer.
于是Neil用锤子砸它
That was successful, it shattered the bits,
的确 它变成了碎片
but there was absolutely no evidence that the metal had changed.
但绝对还没有证据证明是金属发生了变化
It was just Neil’s power that smashed it.
只是尼尔用力砸出的效果
So we then tried a different experiment,
于是我们做了另一个试验
melting the tin,
将锡熔化
and pouring the molten tin, the liquid tin into liquid nitrogen.
将熔化的锡 液态锡倒入液氮中
The thinking here was that if we froze the liquid quickly,
想着如果我们快速冷却液态锡
it would go into the unstable form directly
它就会跳过金属的那一步
without going through the metallic one.
直接成为不稳定晶格
So it was really quite spectacular when it went in.
液锡倒入时的景象真的很壮观
There were great plumes of vapor,
蒸汽滚滚
vapor, water vapor as the nitrogen evaporated.
液氮蒸发时产生大量的蒸汽 水汽
And when we took it out,
当我们拿出锡时
it was a rather beautiful shape of long piece of tin.
可以看到它是一块相当漂亮的长条形锡
But it was the shape of the test tube, so it looked quite artistic.
但因为它是试管的形状 所以看起来很有艺术感
But it didn’t demonstrate what we wanted.
然而这并不是我们想要看到的结果
We thought perhaps we were being a bit impatient,
或许我们应该多点耐心
so we left it in liquid nitrogen overnight.
于是我们把它放在液氮里过夜观察
Wound a piece of string, in case it crumbled away.
并系上了绳子以免它粉碎取不出来
And sadly, when we took it out the next day,
可惜的是 第二天我们把它拿出来时
still hadn’t transformed.
它还是没有变化
For once, we’ve been completely unsuccessful.
这一次 我们的实验完全失败了
I think that when we did,
我认为是我们做实验时
we’ve done it at too low a temperature.
实验温度过低导致的
You probably need it, a bit below freezing point of water,
实验所需温度应该是 略低于水的冰点
minus 10, minus 20 degrees centigrade,
零下10到20摄氏度左右
and when it’s really cold liquid nitrogen temperature,
当液氮温度过低
the atoms don’t have enough thermal energy to rearrange.
锡原子就没有足够的能量进行重排
If we left it in liquid nitrogen for a couple of years,
倘若我们把金属锡在液氮里放上几年
perhaps something would happen.
或许会发生点什么变化
So as well as bronze,
和青铜一样
there’s a very well-known alloy of tin called pewter.
白镴 也就是众所周知的锡合金
Originally it was tin and lead, it’s now tin with other metals,
它原本是锡铅合金 而今则是锡和其他金属合金
It’s particularly famous in Malaysia.
白镴在马来西亚特别有名
You get many souvenirs.
你可以看到很多的纪念品
And when I was in Malaysia,
我在马来西亚的时候
I was given this plate made of pewter.
就收到过一个白镴制的盘子
And the reason why people like it,
人们喜欢白镴
is because you can melt it quite easily
是因为它很容易熔化
and make it into elaborate shapes,
还可以制成精致的形状
like the pattern on this plate.
就像这个盘子上的图案一样
Now we really haven’t talked about the chemistry yet.
至今我们还没有谈到锡的化学性质
Tin is in the same group as carbon,
锡与碳同族
so it has four electrons in the outer shell.
最外层有四个电子
But unlike carbon, it can either use two of these electrons
但与碳不同的是 锡既可以用两个电子成键
or four of these electrons for bonding.
也可以用四个电子成键
When it uses two electrons,
当它用两个电子成键时
it forms, say tin dichloride, stannous chloride,
可以形成 比如二氯化锡 氯化亚锡
which is a salt rather like sodium chloride.
这种和氯化钠很像的盐类
So it dissolves in water,
所以它溶于水
makes a slightly cloudy mixture if you put too much in, but it dissolves,
若二氯化锡过量会有轻微混浊 但会溶解
but it will not dissolve in organic solvents, like cyclohexane.
然而它不溶于有机溶剂 如环己烷
On the other hand, if you use four electrons,
另一方面 它若以四个电子成键
you can make compounds like tin tetraiodide
就可以合成化合物 比如四碘化锡
which is one of the compounds
四碘化锡是学生在
our students make in the first year lab,
入实验室第一年要制备的化合物之一
and we had two samples made by students
我们有两个学生制备的样品
and you can see the colors are a bit different,
你可以看到颜色略有差异
because one made a purer sample than the other.
原因在于其中一个样品纯度更高
The tin tetraiodide is like an organic compound,
四碘化锡类似于有机化合物
if you put this one in water,
如果将它放入水中
the tin-iodine bonds react with the water,
锡碘键就与水反应
so you get hydrogen iodide which you can’t see.
产生不可见的碘化氢
And you get a precipitate of tin oxide, which is white.
以及白色的氧化锡沉淀
If you put it in an organic solvent, it dissolves,
四碘化锡溶于有机溶剂
so you get a nice yellow solution.
形成漂亮的黄色溶液
I won’t say any more or you might cheat, when you’re a student here.
我就不多说了 要不本校生就能作弊了
Tin oxides are important
氧化锡是
in screens on smart phones and similar things
智能手机屏幕和其他显示屏幕的重要成分
because this display consists of a material
因为屏幕有一种金属材料
which is sandwiched between two electrodes,
是夹在两个电极之间的
And obviously the electrode through which you’re looking
显而易见 你现在盯着的电极
has to be transparent,
必须是透明的
and indium tin oxide,
氧化铟锡
that’s a mixed oxide of indium and tin,
是一种铟和锡的混合氧化物
is electrically conducting but is transparent.
它能导电 但它是透明的
So indium tin oxide is a key component
因此氧化铟锡就成为了
of most smartphones and other displays.
大多数智能手机屏和其他显示屏的重要成分
So if you’re watching this you’re probably watching it
因此倘若你正在看这个视频
through a thin film of indium tin oxide.
你很可能是通过氧化铟锡薄膜观看的
The final application of tin
我想告诉你的 锡的最后一个应用
that I want to tell you about involves ships.
是关于船舶的
This is a wooden ship,
这是一艘木船
but it’s the only one I could find.
但这是我能找到的唯一一艘船了
When the ship is made,
当船在建造的时候
obviously the bottom of the ship is absolutely clean,
显而易见船底绝对是干净的
but as it sails arund the seas,
但当它在海上航行时
various marine organisms, mussels, barnacles and so on,
各种海洋生物 贻贝 藤壶等等
fix themselves to the bottom of the ship, and start growing.
附着在船底 开始生长
So eventually the bottom of the ship looks rather like my hair
最终船底看起来就特别像是我的头发一样
with covered in these marine organisms.
被这些海洋生物所覆盖
And this greatly slows down the ship.
这将大大地降低船速
It doesn’t go through the water so easily.
船舶航行起来也就不那么方便了
So for centuries people have tried different sorts of coating on the bottom of ships,
所以几个世纪以来 人们一直尝试涂上不同种类的船底涂层
for so called antifouling to stop organisms growing on them.
用于所谓的防污 以阻止海洋生物的生长
A very successful method is involved using organotin compounds,
一种行之有效的方法就是使用有机锡合成物
usually derivatives of tributyl tin.
通常是用三丁基锡的衍生物
These are very effective in preventing growth on the bottom of the ship.
这些都能有效阻止船底海洋生物的生长
The problem is that the tin can leach,
问题是 锡会浸出
dissolve off the bottom of the ship, and particularly near ports.
从船底溶出 特别是在港口附近
Because there are a lot of ships there,
因为那里有很多的船只
and they spend quite a lot of the time there.
而且会停留很久
And when the tin comes out,
当然 锡渗出时
of course, it stops the organisms,
会阻止海洋生物
the barnacles fixing onto rocks and all sorts of things.
藤壶附着在岩石和其他之类的东西上
So in recent years, there’s been quite a strong movement,
所以近些年来 人们发起了声势浩大的运动
to stop using tin in antifouling paints,
来阻止锡在防污漆方面的应用
and to use clever paint chemistry
呼吁用更好的化学油漆
to make the bottom so smooth that nothing can stick to it.
使船底变得光滑 生物都无法附着
There you go and to think I thought a video about tin would be boring.
你可能会觉得锡的视频很无聊
As you probably know we’ve made videos about all the elements on the periodic table,
你可能知道我们做过元素周期表上所有元素的相关视频
But, like the one you just watched then
但是 就像你刚刚看到的视频
we’re redoing them making them bigger and better.
我们一直在重复修改这些视频以求做得更大更好
If you’d like to support us, help us make those new videos,
如果你支持愿意支持我们 帮助我们制作这些新视频
like the people whose names you see on the screen at the moment,
像你现在在屏幕上看到的那些人一样
you can back us on Patreon, go to patreon.com/periodicvideos,
你可以通过Patreon支持我们 登录网址patreon.com/periodicvideos
Patreon supporters occasionally get little extra goodies.
Patreon的支持者偶尔还会获得一些额外的好处喔
For example, I am about to share with them this video about the professor’s tie collection.
比如说 我会和他们分享关于教授收藏领带的视频
You haven’t lived until you’ve seen a video about the professor’s tie collection.
俗话说看过教授收藏领带的视频才算真正活过
Anyway there are links down in the video description.
总之 这些在视频简介中都有相应的链接
Thank you so much for watching and we’ll be back soon.
感谢您的收看 再会

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  • 2021-08-24如果毒药过期,它的毒性是会变得更强还是更弱?毒药是自然界中的有害物质 而肉毒杆菌素是地球上最致命的毒药 只需几毫微克就能杀死一个成年人 如果服用不当 我们周围的任何东西都可能成为毒药 人们因为喝水过多而死亡 这种现象被称为水中毒或水过多 那么 毒药过期后会发生什么呢? 这就取决于是哪种毒药了 许多毒药如杀虫剂和除草剂 会随着时间的推移逐渐分解 进而丧失毒性 但是这个过程耗时很长 而有些毒药的效期设定 是出于相反的原因 它们会分解并产生更多..

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