How can I make “hot ice” (sodium acetate)?
- Chemical reactions
- Crystallization and recrystallization
- Colligative properties
- Pan with cover
- Microwave or stovetop
- Vinegar (1 liter)
- Baking soda (4 tablespoons)
- Pour the vinegar into a pan, and very slowly (a little bit at a time) add the baking soda. As you may already know, this reaction will produce large amounts of bubbles (carbon dioxide gas), so you’ll need to add this very slowly. This reaction will produce a solution of sodium acetate in water. Sodium acetate is produced according to the chemical equation:
Na+ [HCO3]− + CH3 – COOH CH3 – COO−Na+ + H2O + CO2
- Bring the solution to a boil. Allow the solution to continue to boil until a skin or film begins to form on the surface of the solution. This will require heating for a significant amount of time (perhaps, up to an hour), until a large fraction of the water from the vinegar has evaporated. Our goal here is to form a very concentrated hot solution of sodium acetate. You’ll recall from our discussion of colligative properties that the solubility of a solute is higher at higher temperatures. As we reduce the volume of the water, the sodium acetate will not evaporate, and we will be left with a concentrated solution at high temperature.
- When you notice a film start to form on the surface, remove the pan from the heat, and cover it to prevent further evaporation. Place it on the countertop or in the refrigerator to cool. If you see any crystals begin to form, add a small amount of additional vinegar (or, if you are out of vinegar, use water) and stir the solution so that they dissolve.
- You now have a supercooled solution of sodium acetate that can crystallize out of solution readily if a crystallization nucleus is present.
- You can now slowly pour the first few drops of the cooled solution onto a dish, and it should begin to crystallize rapidly. If it doesn’t, try dragging a fork or knife along the dish to make a tiny scratch, or give the liquid a moment to evaporate a little so that the sodium acetate begins to crystallize before you begin to pour. As you continue to pour, the liquid should continue to crystallize as it contacts the crystals already formed on the dish. This is similar in spirit to how purification takes place during a recrystallization (see “The Modern Chemical Lab”). If you feel the crystals, they will be warm to the touch, since the crystallization is an exothermic process (it gives off heat). This is why it’s called “hot ice,” but now you know it isn’t really ice—it’s sodium acetate—and you know how to make it.
This is a web preview of the "The Handy Chemistry Answer Book" app. Many features only work on your mobile device. If you like what you see, we hope you will consider buying. Get the App