DIY Hand Warmer Using a Simple Chemical Reaction

Last week, our chemistry teacher introduced us to a fascinating chemical reaction that produces a gentle yet long-lasting heat. She explained that this reaction is safe, and we even tested it by mixing the ingredients inside a plastic bag. That moment reminded me of the goal of the Stay Warm contest, because, thanks to that simple reaction, my hands stayed warm that day!

In this instructable, I will show you how to create your own DIY hand warmer using safe materials. This project is perfect for cold days and educational experiments.

Materials Needed

1. Polyacrylamide (water-absorbing crystals)
2. Iron powder
3. Calcium chloride
4. Water
5. Sealable plastic bag (like a Ziploc bag)
6. Spoon
7. Latex gloves (for safety)

In Spain you can buy them here:

1. Polyacrylamide
2. Iron powder
3. Calcium chloride

Start by adding four spoonfuls of polyacrylamide into the sealable plastic bag. Always wear latex gloves while handling chemicals to protect your hands.

Pour a small amount of water into the bag. The goal is to let the polyacrylamide absorb the water completely. Stop adding water once the texture turns into a soft, gel-like consistency, similar to a squishy pillow.

Once the polyacrylamide has expanded, add two spoonfuls of iron powder and mix everything thoroughly.

At this stage, a slow oxidation reaction begins. When iron comes into contact with water, it oxidizes (rusts) and releases heat. However, this process is quite slow on its own.

To speed up the oxidation reaction, add four spoonfuls of calcium chloride (double the amount of iron powder used). Calcium chloride enhances the reaction in two main ways:

1. It increases the temperature of the water in the polyacrylamide, promoting faster iron oxidation.
2. It provides chloride ions (Cl⁻), which act as oxidizing agents, making iron rust more quickly and generating heat faster.

Essentially, calcium chloride helps kickstart the process, making the heat release more noticeable and effective.

Once all the components are inside the bag, seal it and wait for a few minutes. The mixture will start to generate heat. To measure the temperature, insert a thermometer into the mix—it should reach around 40°C (104°F), which is warm enough to keep your hands cozy without causing burns.

Thank you for reading my instructable! I hope this project sparks creativity and inspires you to explore the science behind heat-generating chemical reactions. Let me know if you try it out, and feel free to share your results. Stay warm and keep experimenting!