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Author Topic: magical properties of tomato soup  (Read 3054 times)

paul.fr

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magical properties of tomato soup
« on: 11/10/2007 15:01:31 »
Last weeks podcast reminded me of something I do whilst warming tomato soup. I have a cooker with electric hobs, now when the hobs are at their maximum heat I always flick a bit of soup on them.

The soup forms what looks like a perfect sphere and whizzes off around the hob ending up in the centre. Why does it form the sphere in the first place and why does it circle the hob until it ends up in the middle?


 

Offline daveshorts

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magical properties of tomato soup
« Reply #1 on: 11/10/2007 15:54:42 »
This is a property of the water in the soup rather than the soup itself. When a liquid hits a surface that is much hotter than its boiling point it will immediately boil on contact. This produces a layer of gas underneath the liquid which the liquid floats on. Effectively the droplet has it's own hovercraft, and it tends to skitter about as the gas isn't always released evenly so it can act as jet propulsion.

Exactly the same thing happens if you pour liquid nitrogen onto a floor or put droplets of water on a hot AGA. I would recommend water as opposed to tomato soup for experiments as it makes less mess!
 

Offline JimBob

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magical properties of tomato soup
« Reply #2 on: 11/10/2007 18:15:29 »
In plain English, what are "hobs"? Or an AGA, for that matter?
 

Online Bored chemist

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magical properties of tomato soup
« Reply #3 on: 11/10/2007 19:22:40 »
In plain English they are hobs and an Aga. I'm afraid I'm less sure about the plain American; this might help.
http://en.wikipedia.org/wiki/AGA_cooker
The hob is the heated metal plate on the top that you cook stuff on.
This might tell you about the boiling water.
http://en.wikipedia.org/wiki/Leidenfrost


 

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magical properties of tomato soup
« Reply #4 on: 11/10/2007 20:13:12 »
Thank you for the first two references. I knew about the droplets - I just couldn't picture the cooker or how it worked.

 

lyner

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magical properties of tomato soup
« Reply #5 on: 12/10/2007 15:14:04 »
Two nations separated by a common language.
 

paul.fr

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magical properties of tomato soup
« Reply #6 on: 12/10/2007 23:56:42 »
I would recommend water as opposed to tomato soup for experiments as it makes less mess!

you are correct, Dave. But tomato soup just looks nicer than water. It's also easier to see.
 

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magical properties of tomato soup
« Reply #6 on: 12/10/2007 23:56:42 »

 

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