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-   -   wierd siency stuff (https://www.homemadeturbo.com/general-discussion-6/wierd-siency-stuff-84137/)

jacob 09-20-2007 10:58 PM
wierd siency stuff
 
wtf is this???

http://www.collegehumor.com/video:1776285/

b18. 09-21-2007 12:16 AM
Re: wierd siency stuff
 
It's a percipitate reaction with oxygen. Sodium Acetate I believe? I'm not sure really.

aero 09-21-2007 01:53 AM
Re: wierd siency stuff
 
Actually I don't believe it has anythign to do with oxygen. I believe its a super cooled liquid. Freezing actually releases heat, since it would be a solid at room temperature, it just requires a shock, or a crystal of the solid form to start a chain reaction. Sodium Acetate is used in those reusable heat packs. They are sealed, with no oxygen and are activated by bending a metallic disc that creates an audible click and shockwave. The solidifying action propagates outward from the disc, and within a couple seconds the whole packet is solid, and very hot.


Edit, I was pretty close. http://en.wikipedia.org/wiki/Sodium_acetate
Sodium acetate is also used in consumer heating pads or hand warmers and is also used in "hot ice". When sodium acetate trihydrate crystals (melting point 58 °C) are heated to around 100 °C, they melt. When this melt cools, it gives a supersaturated solution of sodium acetate in water. This solution is capable of supercooling to room temperature, well below its melting point, without forming crystals. By clicking on a metal disc in the heating pad, a nucleation center is formed which causes the solution to crystallize into solid sodium acetate trihydrate again. The bond-forming process of crystallization is exothermic, hence heat is emitted.

Bone1 09-21-2007 03:29 AM
Re: wierd siency stuff
 
nerds

crx2fast 09-21-2007 09:27 AM
Re: wierd siency stuff
 
Originally Posted by Mista Bone
nerds
seriously.. nerd alert! :P

pretty cool though

b18. 09-21-2007 04:45 PM
Re: wierd siency stuff
 
Originally Posted by aero
Actually I don't believe it has anythign to do with oxygen. I believe its a super cooled liquid. Freezing actually releases heat, since it would be a solid at room temperature, it just requires a shock, or a crystal of the solid form to start a chain reaction. Sodium Acetate is used in those reusable heat packs. They are sealed, with no oxygen and are activated by bending a metallic disc that creates an audible click and shockwave. The solidifying action propagates outward from the disc, and within a couple seconds the whole packet is solid, and very hot.


Edit, I was pretty close. http://en.wikipedia.org/wiki/Sodium_acetate
That's pretty freaking awesome. I forgot that a precipitate reaction can only occur in a solute anyway. :S


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