视频文本

So we like to know if there are double bonds in our food molecules
因此我们希望知道食物分子中是否具有双键
but how is that determined?
但如何知道呢
So this is what a "happy" carbon hydrogen molecule looks like
一个非常"开心"的碳氢化合物分子是这样的
but in some cases there are not enough hydrogen atoms
但有时，氢原子数目不足
and the carbon will have to double bond with another carbon to share electrons
碳于是会同另一个碳之间形成双键
This molecule
这个分子
is more reactive than this one
比这个分子反应性更强
because a carbon-carbon double bond
因为碳碳双键
is not as stable as a carbon-carbon single bond
没有碳碳单键稳定
Now let's watch as MIT's Dr. John Dolhun uses bromine
下面来看MIT的John Dolhun博士如何使用溴
to test for the presence of double bonds in a big slab of bacon
来测试一大块培根中是否存在双键
Here he is at the Cambridge Science Festival
这是他在剑桥科学节上的演示
I'm gonna turn on my burner here
我将打开我的燃烧器
OK, there we go
好了
So I'm gonna take my bacon
我夹起这块培根
Basically shake it up a bit
放在里面摇一摇
You can see the red color of the bromine is going away
可以看到，红色的溴消失了
So Dr. Dolhun heats up a piece of bacon
Dolhun博士先是给一块培根加热
and adds it to a flask filled with bromine
然后将它放入到充满溴的烧瓶中
Bromine reacts with anything that has a carbon-carbon double bond
溴会同任何具有碳碳双键的物质反应
This includes the acrolein that's produced when you cook bacon
包括加热培根时生成的丙烯醛
which looks like this
丙烯醛是这样的
as well as the unsaturated fat that's already present in the bacon
还包括培根中已经存在的不饱和脂肪
Unsaturated fats are fat that have carbon-carbon double bonds
不饱和脂肪是具有碳碳双键的脂肪
Fully saturated fats have no carbon-carbon double bonds
完全饱和脂肪是没有碳碳双键的脂肪
They're all carbon-carbon single bonds
其中全都是碳碳单键
and they're the ones that are bad for you
饱和脂肪对人危害较大
The breaking of the double bond looks like this
双键的断开是这样的
We can tell that the reaction happens because the red color disappears
我们通过红色的消失知道反应发生
That's the bromine reacting with those carbon-carbon double bonds
这是溴同碳碳双键的反应
In our video recording of the experiment, it's hard to see the color change
实验视频录制中，颜色变化比较难看清
So watch again very closely
所以请大家再仔细看一遍
Hope you enjoyed the video. I'll see you next time
但愿大家喜欢这个视频，下次再见

视频及简介

视频简介：

魔术背后的化学系列视频展示了一些化学实验演示，这些化学实验都非常精彩有趣，创造出各种蒸汽、响声、闪光等引人注目的效果。视频中详细解释了实验背后的科学知识，通俗易懂，寓教于乐。