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The Sodium Acetate “Hot Ice” Experiment
Materials:
Hot Plate
Magnetic Stir Bar
250 mL Erlenmeyer Flask
Spatula
Watchglass
75 mL of Acetic Acid (Vinegar)
Approximately 0.5-1.0 gr of Na2HCO3Sodium Bicarbonate (Baking Soda)
Procedure:
1. In a saucepan or large beaker, add baking soda to the vinegar, a little at a time and stirring between additions. The baking soda and vinegar react toform sodium acetate and carbon dioxide gas. If you don't add the baking soda slowly, you'll essentially get a baking soda and vinegar volcano, which would overflow your container. You've made the sodiumacetate, but it is too dilute to be very useful, so you need to remove most of the water.
2. Boil the solution to concentrate the sodium acetate. You could just remove the solution from heat onceyou have 65-70 mL of solution remaining, but the easiest way to get good results is to simply boil the solution until a crystal skin or film starts to form on the surface. This took me about an hour onthe stove over medium heat. If you use lower heat you are less likely to get yellow or brown liquid, but it will take longer. If discoloration occurs, it's okay.
3. Once you remove the sodium acetatesolution from heat, immediately cover it to prevent any further evaporation. You should not have any crystals in your solution. If you do have crystals, stir a very small amount of water or vinegarinto the solution, just sufficient to dissolve the crystals.
4. Place the covered container of sodium acetate solution in the refrigerator to chill.
5. To demonstrate supercooling,crystallization, and heat release you could:
* Drop a crystal into the container of cooled sodium acetate solution. The sodium acetate will crystallize within seconds, working outward from where you added thecrystal. The crystal acts as a nucleation site or seed for rapid crystal growth. Although the solution just came out of the refrigerator, if you touch the container you will find it is now warm or...
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