Step-by-step tutorial
Step 1
Gather the materials to make your hot ice hand warmer!
Step 2
Pour 3 cups of vinegar into the pot. Slowly add 3 tbsp of baking soda into the mixture. Add a little bit at a time. We found that large scoops will cause the mixture to bubble out of the pot!(If you want to make more handwarmers, you can increase the amount by adding 1 tbsp of baking soda per 1 cup of vinegar.)
Step 3
Look out, this step can get smelly, so make sure you work in a well ventilated area!Place the pot over the stove, and boil it on medium heat for about 30-60 minutes.As the liquid reduces you'll start to see crystals form on the walls of the pan. Once the liquid has reduced down to about 25% of the initial amount, look out for a thin layer of film over the surface. Once you see the film, turn off the heat. Transfer the liquid to a clean jar, leaving the crystals behind. Your solution will probably be a light yellow color.
Step 4
When the pot has cooled down, carefully scrape the white crystals off the walls and into a baggie. You want to get just the dry crystals, not the solution.
Step 5
Now check on your jar of hot ice solution. While it's still warm, pour it out into a second baggie. You may want to double bag it to prevent leaks.
Step 6
Place the hot ice solution bag into the freezer for 10 to 15 minutes. Once the bag is chilled, you're ready to use your hand warmer.To activate the hot ice, carefully open the baggie with the solution and drop in a small pinch of the white crystals you scraped off the pot. Instant hand warmer!Your hot ice hand warmer is reusable as well. Just heat up the mixture again. Once it becomes a liquid, pop it in the freezer for a few minutes and it'll be ready to use again.
Learn more
What's going on?
When vinegar and baking soda mix, they form a chemical called sodium acetate. That's your hot ice!One interesting thing about sodium acetate is that the freezing point of the crystals is really high over — 130° F. (Compare that to water, which has a freezing point of 32° F.) When you heated your sodium acetate solution, you took it above the freezing point. When you separated out the crystals and cooled it down, you took the solution below its freezing point. But, you did it in such a way that the sodium acetate was unable to form crystals or freeze.When you dropped the crystals into the solution, that allowed the liquid to crystallize fast! This process of crystallization is an exothermic reaction, which means it releases a lot of heat.In fact, this reaction is how many commercial heating pads and hand warmers work!