Placeholder Image

字幕列表 影片播放

  • This is a special experiment that Neil has wanted to do for nearly forty years.

  • He saw it done by his teacher and he's always wanted to repeat it.

  • The experiment is very simple.

  • It consists of a test tube in a test tube rack, filled nearly to the top with Diethyl Ether.

  • The point about Diethyl Ether is that it's very volatile.

  • Its boiling point is just above room temperature.

  • And so you can get it to evaporate by blowing air through it.

  • But it's better to use Nitrogen, because it's pretty inflammable.

  • Think for a moment why atoms in the gas phase form a liquid.

  • And they form a liquid because the atoms or molecules are attracted to each other.

  • And they're attracted to a denser state, which is a liquid.

  • So when you evaporate a liquid, you have to put in energy to pull those molecules apart.

  • And because Diethyl Ether is not a very high boiling point liquid,

  • you don't have to put in all that much energy, but you still have to put in some energy.

  • And it comes from the temperature of the Ether and from the temperature of the room.

  • So what happens is, as you blow the Nitrogen through the test tube, it starts cooling down.

  • If you didn't have the Nitrogen, the vapor, which is quite heavy, would just sit in the top of the test tube

  • and no more evaporation would take place.

  • So the Nitrogen is stirring things up and blowing the vapor away.

  • Now, Neil got a bit bored because it was rather slow,

  • turned up the flow of Nitrogen, and you can see really beautifully,

  • how the Ether vapor comes out of the top of the test tube,

  • and because it's heavier than air, and it's cold, it then floats down the side of the test tube.

  • With the thermal imaging you can see this vapor really nicely, with the naked eye, you can see nothing.

  • As the liquid evaporates, you need to put in the so-called latent heat of vaporization to get the vapor to come out.

  • We're not having any source of heat, so the heat is coming from the liquid itself, and its temperature drops.

  • So if you look at the thermal imaging you can see the color of the Ether changing as it gets colder and colder.

  • And the scale is on the side of the picture.

  • Now, the part that Neil really remembers is that after the teacher had done this experiment for a bit,

  • he squirted some water onto the outside of the test tube.

  • Now remember, the test tube is pretty cold.

  • So the water cooled down and actually froze.

  • So ice was formed in a pool at the bottom of the outside of the test tube.

  • And not only was it formed, but effectively sealed or glued the test tube to the test tube rack.

  • And the image that really stuck in Neil's mind was his teacher, Mr. Manser, lifting up the test tube

  • and the whole rack coming with it.

  • Neil thinks it's pretty remarkable that you can freeze water just by the evaporation of the Ether.

  • I'm slightly less surprised, because in one lab where I was working,

  • somebody dropped a whole large bottle of Ether and it splashed on his trousers.

  • And the evaporation nearly froze his legs.

  • Another technician dropped a bottle of Ether, it caught fire and burnt off his eyebrows.

  • But that's another story.

  • We thank Google's Making & Science initiative for helping us make this video.

  • If you want more information about the initiative, look down in the video description.

This is a special experiment that Neil has wanted to do for nearly forty years.


單字即點即查 點擊單字可以查詢單字解釋

B1 中級

用二乙醚冷凍水 - 視頻週期表 (Freezing Water with Diethyl Ether - Periodic Table of Videos)

  • 0 0
    林宜悉 發佈於 2021 年 01 月 14 日