What You Need:
- Pencil sharpener
- Self-sealing sandwich bag
- 1 tsp. salt
- 2 tbsp. water
- 2 tbsp. vermiculite (garden store)
- 2 tbsp. iron powder (hobby shop)
- 2 tbsp. pulverized activated charcoal (pet store)*
*If you can’t find pulverized charcoal, put coarse charcoal in a bag and mash it with a hammer.
What You Do:
- Have your child sharpen the pencil and crush the shavings until you have about 3 tablespoons of pencil shavings.
- Help him mix all of the ingredients except the water together in a bowl, then pour the mixture into the sandwich bag.
- Add the water to the bag, then seal it up tighly, making sure you allow air to get in.
- Squeeze and agitate the bag, then observe the results. What happened? How quickly did the mixture begin to heat up?
Where does this mysterious heat come from? A long-lasting chemical reaction occurs when oxygen (air) mingles with iron. This is called an exothermic reaction, because it produces heat.
All of the ingredients in this "trick" play a role! Iron is the energy source. The chemical reaction is accelerated by the salt and the charcoal. Water serves as the combining medium, which is evenly diffused by the vermiculite. Lastly, sawdust insulates the hand warmer so that it retains heat.