How can ice freeze without bringing it to freezing temperature? Make instant hot ice, of course. Impossible? Possible! By making crystals dissolve in hot water and letting the solution cool off, you can keep the crystals in aqueous form until you "trigger" the solidification with your finger. The mixture looks like ice and, because the crystallization is exothermic, the ice-like substance releases heat!


Steps

1. Dissolve the sodium acetate trihydrate crystals. Dissolve as much sodium acetate as you can in hot, almost boiling water.
   
   
   
   
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     Scoop the sodium acetate and place it in the pan. Shown here, it is gel-like because it was taken from a warming pad, but in most cases, it's in powder form. About a cup of sodium acetate is a good place to start.
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     Add water into your pan. You want to add just enough so that the sodium acetate dissolves. The key is to "pack" or "supersaturate" the water with sodium acetate, so don't add too much water. The less water you add, the more dense the solution will be, and the better the crystals.
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     Heat the mixture until it's almost boiling.
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     Stir the mixture constantly. This is where you actually dissolve the crystals. All of the powder should dissolve into liquid form until the solution can't "hold" any more, so there should be a little extra undissolved powder at the bottom. If there isn't, keep adding powder until the solution gets to that point. Remember, you want to pack as much sodium acetate in the solution as you can. It is very important to keep on stirring at this point of the project.
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   When dissolved, pour the solution into a glass of any size. Make sure the remaining undissolved sodium acetate stays within the pan. Do not let undissolved material get into the glass.
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   Cool the glass of the solution in the refrigerator for an hour or even 30 minutes (use your best judgement). What is happening here is that you're bringing the temperature below the temperature at which the solution is saturated. Normally, dissolved crystals crystallize again once you bring them below this point, but in this case, because you have the sodium acetate in a supersaturated solution, it "supercools" meaning that it goes below the normal temperature of crystallization without actually crystallizing.
4. Pour your solution into a tray or container. Be careful not to spill any, and make sure the solution doesn't come into contact with any solid sodium acetate. This step is optional, but in case you want a better container in which to view the hot ice formation, here's your chance.
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   Touch the solution with a bit of the solid sodium acetate on your fingertip or a toothpick. The solution should turn into a solid as soon as you touch it. Make sure the touch is quick, as you don't want a chunk of ice stuck to your finger! By introducing a "seed" crystal, you just created a nucleation center, triggering the process of solidification.
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   Touch the newly formed solid. It should be warm (130°F, 54°C) because the formation of crystals releases energy, and this is why sodium acetate is used in heating pads and hand warmers.

Tips

• If you don't have sodium acetate, you can make your own from baking soda and vinegar, but it's time-consuming. Keep adding baking soda to vinegar until it stops fizzing; this reaction yields a diluted solution of sodium acetate and water. Then boil off all of the water to make sodium acetate crystals, which you can treat like the powder as described in the instructions above.
• You can make ice sculptures if you pour the solution onto a pinch of the solid crystals. The solution will turn into a solid when it comes in contact with the crystals, and will continue to solidify while you pour. The ice will soon tower up!
• Some chemistry notes:
  
  
  • The sodium acetate crystals dissolve; they do not melt (dissolving and melting are entirely different processes).
  • Also, dissolved crystals are aqueous; they are not liquid.

Warnings

• Do not touch the solution until it's cooled!
• Also be careful not to inhale any solution. It's never a good idea to "smell" chemicals.