B1 中級 英國腔 31167 分類 收藏
Hi, I'm Eddie. I'm a formal communicator here in At Bristol
In our water cycle workshop we talk about 'Supercooled Water'
I've got a demo here for you that's great to try at home.
So, you may notice on those cold winter evenings people place salt
out on the streets and pavements, because salty water can go well below zero degrees
and remain liquid it freezes.
We're going to try and get a bottle of fresh water to get well below zero degrees C
but still remain a liquid.
For your super cooled water demo
you need lots and lots of crushed ice,
a small bottle of water
a beaker with round about 100ml of tapwater
plenty of table salt,
teaspoon, and a metal cylinder to place all of your ingredients inside.
First thing I'm going to do is to pour plenty of crushed ice
into the bottom of my metal cylinder then
I need five teaspoons salt to sprinkle around
I'm going to now place my small water bottle inside
Around that water bottle now i need to pack in
as much ice as possible.
Now, another 5 spoons of salt
Next, i'm going to take 100ml of water
and add 5 teaspoons of salt to this
Stir the mixture around
Now i'm going to pour this salty water all around the ice
around my bottle
Now, if you've got any room
add some more ice on top
What we do now is just sit and wait for a good 30 minutes
and then our supercooled water should be ready
The reason why i can get a bottle of fresh water below zero degrees without freezing
is because in our bottled water,
we have nonucleation points. A nucleation point is simply
any impurities inside that bottle of water which is going to allow
ice crystals to form around it. Now when I have my bottle of fresh water that is
liquid but below zero degrees, if i cause a disturbance
like pouring that water over an ice cube, I'm going to create many nucleation sites
and that liquid will turn to ice instantly.
it's been about 30 minutes now, so let's see if our super cooled water
is ready to make some instant ice
So there you go. Instant ice, fantastic experiment.
Why don't you try at home?


天氣熱想喝冰?教你做出速凍冰塊! (How to make instant ice | Do Try This At Home! | At-Bristol Science Centre)

31167 分類 收藏
James 發佈於 2015 年 7 月 6 日    Clément 翻譯    Yvonne 審核
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