Participants will learn how mixing some substances together can create an entirely new substance with new properties. Some topics explored in this activity include: supercooling, nucleation, and exothermic processes.
Materials
- 4 cups of white vinegar (acetic acid)
- 4 tablespoons of baking soda (sodium bicarbonate)
- A pot
- Glass measuring cup
- A dish
- A spoon
- A stove
Framing
As you are going through the steps of this experiment, keep your participants engaged by asking question like, “What do you think will happen if I…?” or “How will we make hot ice with this liquid?”
Instructions
- Pour the 4 cups of vinegar into the pot then, slowly add the baking soda into the pot, one tablespoon at a time.
- Using the spoon, stir the solution until all the baking soda has dissolve and the fizzing has stopped.
- Set the pot on the stovetop (no lid) and bring to a boil at medium low heat, until the solution is reduced by 75% (there is ¾ - 1 cup left). It may take a little over an hour to complete this step, but it’s important to ensure that most of the water from the vinegar is evaporated. You will also notice white powder begin to form on the sides (or yellow-brown if your heat is set higher); you will use this later.
- Remove the reduced solution from the heat, pour it into the measuring cup, and place into the fridge for 30-45 minutes.
- Scrape some of the white powder from the pot and place in the centre of your dish.
- Remove the cooled solution from the fridge and slowly pour it over the tiny pile of white powder of your dish. Watch the hot ice form. Touch it, feel it, break it apart!
Modify
- The solution can be saved and remelted for later use. Try adding food colouring next time.
Safety
- While the hot ice is safe to touch, because of its acidic nature, it can irritate the skin if there are open cuts. In that case, it may best to wear some gloves.
Wrap-up
The liquid solution we created is what you call a supercooled liquid, which means that the solution was cooled down to a temperature where it would normally turn solid but instead stayed liquid. The sodium acetate molecules in the solution are kept apart by the water molecules, but because there a few water molecules in the solution, it wants so badly to be solid that if you add a tiny amount of white powder that isn’t the solution, crystallization will occur – this is called a nucleation site. The white powder we placed on the dish served as a nucleation site when we poured the liquid solution over it. The solution crystallized into ice and released some heat (exothermic process).
Lynch, Noirin. “Hot Ice Science Experiment.” Playdough to Plato. Last updated December 12, 2017. Retrieved May 23, 2018, online from: https://www.playdoughtoplato.com/kids-science-experiment-hot-ice/