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Descrepant Event- A Second Boil

submitted by ed11561
1 decade 6 years ago

The red hot quarter boils methanol, twice... A Discrepant Event is an event that defies eveything you already know. The explanantion- The intense heating allows the copper to mix with (or float up through) the nickel cladding. The sudden release of bubbles is likely an example of the "Leidenfrost" effect. The alcohol forms a vapour layer around the coin slowing the rate at which heat can escape. When the liquid stops boiling, the insulating vapour layer around the coin collapses and the coin-liquid contact is more efficient at transferring heat away from the metal. This results in a sudden rush of bubbles as the coin cools to below the boiling point of methanol. The collapse of the gas layer also reveals the new colour of the coin. This mimics an exothermic phase transition and is a dramatic way to illustrate how a physical (or chemical) change can result in a sudden release of energy.

3 Comments

ashes2flames says...

Am I right in thinking there actually is no second boil but just a release of trapped gas? Or some other secondary chemical reaction that is not boiling?

fissionchips

ashes2flames, that was my initial guess as well but the poster's explanation says otherwise.

I'm trying to understand how the Leidenfrost works here, since I would expect at all times for bubbles to be forming out of the surface gas layer.The buoyancy of the gas should ensure bubble formation even if the liquid doesn't come in contact with the quarter.

Moving this video to ed11561's personal queue. It failed to receive enough votes to get sifted up to the front page within 2 days.

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