CyrusGrey
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Copper quarter video
Maybe this is obvious to all of you, but I am still scratching my head:
http://www.instructables.com/id/Making-A-Copper-Quarter/
What is the explaination for these two phenomena?
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not_important
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I suspect the boiling is first from the simple heat of the coin, the liquid methanol vapourising before it can touch the coin.
The second boiling migt come from one or botrh of two things. After the coins cools enough the liquid methanol touches the coin where it reacts with
the oxides, reducing the cupric oxide and releasing heat. Alternatively the rough oxide coat may provide nucleation centers triggering boiling until
the coin finally cools enough.
The cladding on US coins is 3/4 copper, 1/4 nickel. When heated in air it will oxidise to the mixed oxides I believe. The cupric oxide could be
reduced to red cuprous oxide or even to metallic copper, in either case giving the reddish colour.
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ScienceGeek
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It's called the Leidenfrost effect!
<object width="425" height="355"><param name="movie" value="http://www.youtube.com/v/PCeY7AQ8JzQ&hl=en"></param><param
name="wmode" value="transparent"></param><embed src="http://www.youtube.com/v/PCeY7AQ8JzQ&hl=en" type="application/x-shockwave-flash"
wmode="transparent" width="425" height="355"></embed></object>
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CyrusGrey
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Ah! So thats what it is. I'm going to put this down as a possible chemistry video to make for the HCS.
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ScienceGeek
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Out of pure interest: what's HCS?
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woelen
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Home Chemistry Society, which is discussed elsewhere on this forum.
I am in the process of setting up webhosting and the domain www.homechemistry.org. I already have the domain, now it still needs to be connected to a hosting bundle. Hopefully end of this week or beginning
of next week, it all will be working. Read more in the appropriate thread, just search for HCS and you'll find it.
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ScienceGeek
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Of course! That is so embarassing that I forgot that, as I was a part of the discussion 
Thank you guys 
But, I think that my video on the Leidenfrost effect falls under Physics, and not under chemistry! What do you think?
[Edited on 31-3-2008 by ScienceGeek]
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CyrusGrey
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Physical chemistry. 
I hate to strike a low blow here, but quite a bit of physics is just various branches of chemistry. 
[Edited on 31-3-2008 by CyrusGrey]
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ScienceGeek
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hmmm...would it really fall under physical chemistry? There is no chemical reaction happening, neither on a intermolecular or atomic level...?
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Zinc
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| Quote: | Originally posted by CyrusGrey
I hate to strike a low blow here, but quite a bit of physics is just various branches of chemistry.
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I think it is the opposite of that.
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-jeffB
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| Quote: | Originally posted by ScienceGeek
hmmm...would it really fall under physical chemistry? There is no chemical reaction happening, neither on a intermolecular or atomic level...?
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The evident color changes on the coin strongly suggest redox activity.
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ScienceGeek
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Of course, but that was not my point on making the video.
To show the reduction/oxidation going on, I would place the copper coin half above the metanol 
But if one were to take into consideration the red/ox, then I can agree that it's chemistry we're talking
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