Homemade handwarmers will keep frostbite from your fingers

Brrr…it is cold outside this week. I think that winter has finally arrived here in southern Alberta. There are many ways to keep warm while you are outside enjoying the winter weather. This week, I thought I’d share how to make your own handwarmers to keep your fingers warm and toasty! Let’s get started!

*Remember to ask an adult before doing this experiment.

Materials

zipper sandwich bag iron filings (purchase at the hardware store) measuring spoons measuring cups warm water water absorbing crystals (purchase at craft store)

calcium chloride (in the spice or pickling section at grocery store or in “ice melter”) permanent marker goggles

Procedure

1. Put on your safety goggles.

2. Write on your bag – SCIENCE EXPERIMENT DO NOT EAT. Set aside for now.

3. Measure one cup (250 mL) of water and add 1/2 teaspoon (2.5 mL) of the water absorbing crystals. Allow this to sit for a little while (preferably overnight). 4. Observe now and again. 5. What is going on? 6. Measure 1/4 cup (60mL) of the hydrated water absorbing crystals to the zipper baggie.

7. Add one tablespoon (15 mL) of iron filings to the baggie.

8. Measure two tablespoons (30 mL) of calcium chloride to the baggie as well. 9. Zip the baggie up tight. 10. Squish it all around so you can mix the entire contents of the bag.

11. Once everything is mixed up well, squish ALL of the air out of the baggie and zip back up.

12. Roll the bag back and forth between your fingers.

13. What do you feel?

14. Put this in your pocket on a cold day to keep you warm!

What is going on?

First of all, you probably witnessed something pretty amazing if you observed the water absorbing crystals at all. The water absorbing crystals are quite an interesting substance as they will grow to quite a large size – perhaps even overflow the container they are in. This is because they are made with a superabsorbent polymer and when hydrated (added to water) grow and grow.

As you rub the baggie, it will begin to feel hot due to the chemical reaction that is taking place. First, a bit of background. The reaction in this experiment starts with rust. Rusting is an example of corrosion as the iron metal begins to break down. The reactants in this chemical reaction are iron, water and oxygen and the product or result is iron oxide which we commonly know as rust. In this experiment the water absorbing crystals provide the necessary water to the iron filings in order to start the chemical reaction of rusting. You further add calcium chloride which further produces an exothermic reaction or produces the heat you feel. Pretty interesting reaction from just a few household materials. I hope that these will keep you warm this winter!

Did you know that you could easily make this into a great science experiment? What if you varied the amount of calcium chloride or the amount of iron filings – would it affect the amount of time the hand warmer stays hot? Give it a try!

Teachers - if your school is interested in having a science fair club, make sure you call soon so I can pop by and give you some great pointers!

Patty Rooks is senior scientific consultant at PRAXIS, “Connecting Science To The Community.” Contact Praxis at praxis@praxismh.ca, www.praxismh.ca, Tweet or follow us @PraxisMedHat, or friend us on Facebook.