Sciencemadness Discussion Board

Metal explosions 'driven by charge'

phlogiston - 27-1-2015 at 02:40

Metal explosions 'driven by charge'

and the original paper is here

Goes to show how even common well-known classroom experiments can still yield new findings if you study them closely.

Tdep - 27-1-2015 at 04:15

My god he was right!

Why sodium explodes

I can never get angry at him for being pretentious again. Great work.

[Edited on 27-1-2015 by Tdep]

j_sum1 - 27-1-2015 at 05:01

I saw that too and was going to post it. Thanks phlogiston.
Nice vid Tdep. I like his explanation. I might have to look at some more.

Morgan - 27-1-2015 at 07:39

It would be interesting to test this coulombic idea using an inert atmosphere to see how it goes.

jock88 - 27-1-2015 at 14:57


It reminds me a little bit like the Leidenfrost effect when water is dropped onto a hot surface but I guess that is a driven by something completely different.

Zombie - 27-1-2015 at 22:42

New to this, and I sure don't have the vocabulary yet.

To see if I understand the videos, and the research...
The claim is that an explosion should not occur because a layer of steam or vapor will shield the components perhaps similar to a capacitors film layer.

In my minds eye I see the water vaporizing, and creating more surface area for contact between the components. Given the molecular attractions, and repulsion happening I also see even greater surface area developing to the point of complete immersion in the process.

I think I understand this, ( in a simplistic fashion) and I have to wonder why it is "news". It's the way I thought it worked.

[Edited on 28-1-2015 by Zombie]

phlogiston - 28-1-2015 at 02:50

A layer of mostly hydrogen gas rather than steam should form between the sodium and the water, which would inhibit the reaction.

The new finding is that a charge very quickly builds up on the sodium metal, causing what is known as a 'coulomb-explosion', that is: the repulsion between the positive sodium ions reaches a point where the droplet can not hold together anymore and explodes into jets of smaller droplets.

Morgan - 28-1-2015 at 07:20

Seems like they should try to setup an experiment to measure the supposed charge.

Sort of the same general information but with video and larger images perhaps.
http://cen.acs.org/articles/93/web/2015/01/Sodium-Potassium-...

Drop of sodium/potassium alloy explosion in water
https://www.youtube.com/watch?v=CdFlgnl8rPs

Maybe of interest
"The scheme provides a way to study charge dissociation reactions of molecular dianions that are too short-lived to survive extraction from the ion source."
COULOMB EXPLOSION UPON ELECTRON ATTACHMENT TO A FOUR-COORDINATE MONOANIONIC METAL COMPLEX.
http://www.pubfacts.com/detail/12904017/Coulomb-explosion-up...

[Edited on 28-1-2015 by Morgan]

Zombie - 28-1-2015 at 09:41

Quote: Originally posted by phlogiston  
A layer of mostly hydrogen gas rather than steam should form between the sodium and the water, which would inhibit the reaction.

The new finding is that a charge very quickly builds up on the sodium metal, causing what is known as a 'coulomb-explosion', that is: the repulsion between the positive sodium ions reaches a point where the droplet can not hold together anymore and explodes into jets of smaller droplets.


That is exactly the way I believed it worked. I can not understand how anyone could believe there could be a barrier or shield built between the components. The very same action that creates the explosive force is the same reaction that drive the coulomb effect. A repulsion of particles creating free space for component interaction. That free space allows the molecular attraction to take place. Once that free space is created, and the attraction happens, it is an almost instantaneous reaction because the coulomb effect allowed it to happen

Is this wrong? It just doesn't seem like big news. I thought it was a given.

[Edited on 28-1-2015 by Zombie]

violet sin - 29-1-2015 at 04:01

pretty darn interesting. something that occurred to me was the possibility that the grey cloudy stage where the blue flash happens, could be a second much finer scale eruption of spikes. with that much surface area and electrons being stripped so fast, perhaps it is visible?

just seems like the initial contact would induce a second wave of stripping new metal and explosion of the new structure would be eminent. for some reason I thought about it like a feedback loop getting louder( poor wording yes, but it is ~4am here, sory)

@Zombie : the Na doesn't pull like a magnet to the water prior to contact(no charge), and it did sound plausible that a gas curtain would hamper contact even if not an idealized barrier. so a bald face of sodium presents little surface area by comparison to the observations. the fact that the metal surface would only be slightly etched while gas production would starting/happening would mean more water contact by swirling but still limited Na surface area. really only helping on one side unless the reaction on the waters part was violent enough to tear the Na into smaller pieces. the fact that the metal freaks out and impales the water(!) increasing contact +XXX% would be news to me, and the standard as explained logic of the past. not to mention it is pretty cool.

Zombie - 29-1-2015 at 09:30

Following your lead... I was believing the sodium was pulling the water molecules into itself vs. impaling into the water.
Once one atom is detected the entire molecule in essence goes bat shit ballistic.

I will learn the proper terms in time. For now I'm still learning the concepts..
I guess you could say this is something of an atomic reaction.?.? That,s the way I visualize it. That purple "flash" may be the supposed "barrier" being destroyed. Once that barrier is gone there is nothing to stop the reaction.

If you fellas want... send your science books to Carrabelle Fl. I'll correct them for ya.:D

blogfast25 - 29-1-2015 at 16:32

Quote: Originally posted by Zombie  

If you fellas want... send your science books to Carrabelle Fl. I'll correct them for ya.:D



Start learning and stop being such a twit. It's obvious you neither understand the old understanding nor the new one.

Zombie - 29-1-2015 at 16:39

Perhaps I can not express in the words you prefer but I assure you. It's not as complex as has been accepted.
Given a monkey, and a typewriter I may live long enough to post up the correct words.

The vocab is new to me. The concept is not.

I apologize if my levity offended. I'm just not much of a stuffed shirt, and prefer to smile. Even while learning.:D

phlogiston - 30-1-2015 at 02:30

So, then, consider it a good excercise to really try to understand every detail of this paper. You will only get to fully grasp the terminology if you study it.

If you are indeed not yet familiar with the common vocabulary of chemistry, please do consider that this likely also interferes very much with your understanding of written theory such as was discussed here.

Do not assume too quickly that you perfectly understand everything in your head but can't express it in words. It is fundamental in science to allow for the possibility that your ideas may be wrong. (one should in fact actively try to prove them wrong).

Because to me, it appears as if you have misunderstood the paper and did not fully understand either the old or the new theory of what is going on, even if I squint my eyes and try to see your reasoning between the lines.

So, study. Study more.
Then, when you can demonstrate understanding it, feel free to shout that this paper in a high quality peer-reviewed journal such as <i>nature</i> is completely trivial and uninteresting to you.

Zombie - 30-1-2015 at 08:27

Point taken, and understood. I appreciate your posting that.
Thanks Phlogiston.

Explanation for Alkali Metal/Water Explosion

Boron Trioxide - 2-2-2015 at 16:58

Oops I guess it was already posted under a different name.

[Edited on 3-2-2015 by Boron Trioxide]

Zombie - 2-2-2015 at 17:36

Most of those vids. are in the previous links in this thread.
Your second link does contain more information than the others.

It's a fun topic. Thanks for adding to it!