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暖手宝的工作原理 – 译学馆
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暖手宝的工作原理

How Hand Warmers Work (THERMAL IMAGING) - Periodic Table of Videos

We’re talking about these funny hand warmers in the shape of a heart.
我们今天来谈一下有趣的心型暖手宝
And each one contains a liquid and a little metal clicker
每个暖手宝都含有一种液体和一个金属响片
and the point is that this can generate
关键在于这能产生
quite high temperatures which will keep your hand warm.
相当多的热量让你的手保持温暖
Inside is sodium acetate that is dissolved in water.
暖手宝中的醋酸钠溶液
It’s a very concentrated solution.
是一种浓缩液
Sodium acetate is made up of ions,
醋酸钠是离子晶体
positively charged sodium, negatively charged acetate.
钠离子带正电 醋酸根离子带负电
Positive and negative attract each other
正负极互相吸引
and so you need energy to pull them apart,
需要能量把它们拆开
and you have to imagine a huge array of these.
想象一个巨大的阵型
Millions and billions of these, going alternately, positive, negative and so on.
数以亿计的离子 正负交替排列
But I can’t afford that amount of model.
但我无法提供这么多模型
So I press it down and there we go.
按压金属片 然后松手
If I look at it on the screen
此时通过热成像观察暖手宝
you can see a blob of warmth coming in the middle of the heart.
你能看见暖流从这颗心的中部扩散开
The other heart doesn’t do anything
而另一颗心却无现象
and it reaches in…
我们伸手去摸……
Oh, it’s really getting warm
哇 它真的变暖和了
and it goes up to a temperature about 50 degrees.
温度升高到50摄氏度左右
It’s somehow producing crystals that come out sideways and giving out heat,
它正以某种方式向旁侧析出结晶并散发热量
which lasts for 20 minutes or so.
持续二十分钟左右
What happens is when you click,
当你按压暖手宝时
a tiny particle of something is released.
释放了一个小颗粒
Some people say it’s a bit of metal,
有人说这个小颗粒是一小块金属
others say
也有人说
it’s a tiny crystal of sodium acetate that was trapped on the metal surface.
是附着在金属响片表面的醋酸钠晶体
It doesn’t matter.
这并不重要
You release something
你释放出这种物质后
and as soon as you have that first tiny nucleus, the precipitation takes place.
一旦形成第一批小结晶核 就会产生沉淀
And you can see the crystals spreading out across the hand warmer
你可以看到晶体分散开 遍布整个暖手宝
and the temperature rising.
而且温度会上升
暖手宝是如何制成的……
So, when you drop crystals of sodium acetate into water, the ions separate
把醋酸钠放入水中时 离子随之被拆开
and because they need energy,
因为此过程消耗了能量
the temperature of the water drops and you can see quite nicely with thermal imaging.
你可以通过热成像清楚看到水的温度降低
醋酸钠溶解在水中
If you drop sodium acetate crystals into water the water gets cold.
如果你把醋酸钠放入水中 水温会降低
It’s getting cold because some of the thermal energy, the heat energy in the water,
水温之所以降低是因为这些离子被拆开时
is being used to pull these ions apart.
消耗了水中部分热能
This is a physical change,
这是一个物理变化
so if they come out of solution, reform their crystals,
因此如果它们从溶液中析出 重新形成晶体
you’ll get that energy back.
就会产生热量
So the question is how can you get that energy back in your hand warmer.
问题在于你怎样才能产生暖手的热量
The way you’ve got to do it,
得以成功的方法
is to get as much sodium acetate as possible dissolved in the water.
就是让尽可能多的醋酸钠溶解在水中
And with sodium acetate if you heat the water up
如果对溶液进行加热
you can dissolve more and more of the salt.
你就可以溶解更多的醋酸钠
So if you go almost to the boiling point of water, hundred degrees centigrade,
如果达到了水的沸点 100摄氏度
you can dissolve really a large amount.
你就可以大量溶解醋酸钠
What you would imagine that if you dissolve all this stuff up by heating it,
你会想如果加热溶解所有这些物质
as soon as you cooled it down you would expect it all to come out again.
冷却下来后这些盐会再次析出
But the interesting thing is, that crystals cannot just form in a really clean solution.
但有趣的是纯溶液中不会形成结晶
They need to have tiny particles,
它们需要小颗粒
doesn’t really matter what of,
颗粒是什么实际上并不重要
tiny bit of metal, a tiny crystal to form round.
小块金属 形成的圆形结晶
It’s rather like a crowd forming round a single person.
它很像一群人围着一个人
It has to have something to start it.
必须要从某种物质开始
So if you have a really clean filtered solution, if you cool it down,
因此纯滤液冷却后
the sodium acetate stays in solution
得到的醋酸钠溶液
and that’s what’s inside your hand warmer.
便是暖手宝中所含的液体
So at least your hands will be warm
至少在天气寒冷时走路上班
when you walk to work in the freezing conditions.
你的手能够暖和些
To reuse the hand warmer you have to heat it up again.
你不得不通过再次加热来重复利用暖手宝
So we dropped it into boiling water.
因此我们把它放入沸水中
And quite by chance we noticed that
不仅如此我们还无意间发现
there were all sorts of interesting bubbles and vortices in the surface of the boiling water.
沸水表面产生了各种有趣的气泡和漩涡
So that’s what you have to do to finish it off,
以下就是重复利用所需要做的
just put it in there, leave it for a little while,
把暖手宝静置在热水中一会儿
you take it out and let it relax
取出并让它松弛下来
and it gets cooled down and remains liquid.
冷却之后让其保持液态
And if you heat it for a longish time,
如果你加热稍长一段时间
all the sodium acetate redissolves
所有的醋酸钠会再次溶解
and then if you cool it slowly it will be ready to use again.
待它逐渐冷却下来 便可以重新使用
The problem is that if you don’t heat it long enough
问题在于如果你没有加热足够长时间
and leave just one or two tiny crystals,
而留下了一两个小晶体
it can go off spontaneously and suddenly release its heat.
它就会自发脱落并突然释放热量
It’s not dangerous
这并不危险
but it means when you go to it to warm your hands
但意味着当你用来暖手时
you find it’s fired already.
它已经发烫了

诺丁汉大学 英国·中国·马来西亚
视频来自Brady Haran
额外视频编辑James Hennessy
Thanks for watching this video
感谢观看此视频
and we’d like to thank
此视频的成功制作
Google’s Making and Science team for making it possible.
要感谢谷歌的“科学与制造”团队
If you’d like to see more of the videos they’ve helped create
如果你想看更多他们赞助的视频
there’s a brilliant playlist; there’s links on the screen and in the description.
视频介绍栏里有一个超赞的播放列表和网址
Also if you’d like to see Professor Poliakoff long-awaited appearance
另外 如果您想在我的客观性系列中
on my Objectivity series.
看到期待已久的Poliakoff教授
There are also links for that.
这里也有一个相关的链接
And we’ll be back again soon with more videos with the thermal-imaging camera.
我们很快就会带着热成像相机和更多的视频回来

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视频概述

暖手宝里的液体是过饱和溶液醋酸钠(sodiumacetate,CH3COONa)由于过饱和溶液的浓度太高,所以并不稳定。当扭曲金属的时候,所产生的轻微震动便足以使溶质结晶(crystallize),变成较稳定的固体。然而,这个过程是放热的(exothermic),所以暖手宝开始暖起来。

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翻译译者

Charlie.

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视频来源

https://www.youtube.com/watch?v=QfC9kifJyWI

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