How to Teach Valence Electrons with Handwarmers

I’ve found that the best way to start a lesson on valence electrons isn’t with a textbook—it’s with cold hands and the phenomenon of handwarmers.

In a class recently, we tackled the phenomenon of handwarmers to understand periodicity and how atoms actually combine. I gave the students the warmers, let them feel the heat, and then showed them a thermal imaging video I put together.

Seeing the temperature spike to nearly 47°C(117°F) on screen really drove home the idea that something energetic was happening inside that pouch. We also opened up the pouch so they could see the properties had changed. 

Getting the ideas on the table

We started with Switch-Its on whiteboard tables to create initial models. I love using these because they let the students be messy with their thinking. They identified the big players—Iron (Fe), Oxygen from the air, and the packet itself. At first, their models were just guesses, but it gave them a physical place to start.

The Mini-Lesson

I used the magnetic whiteboard blocks to show them how NaCl formed, I then challenged them to go back to their groups and refine their handwarmer models. This was the best part of the day.

Using the blocks, they could:

• Draw the Lewis-dot structures right on the surface.
• Physically rearrange the blocks to show how the electrons were transferred and how the Iron and Oxygen atoms were actually combining.
• Visualize the transition from separate reactants to the final products that create all that heat.

Watching them "click" the blocks together to represent chemical bonds makes the abstract nature of chemistry make sense. They aren't just drawing circles; they’re building the reaction.