Science Buddies: "Ask an Expert"

I have a student learning about exothermic chemical reactions. He wanted to test whether adding additional iron fillings to homemade hand warmers would create a hotter, longer lasting chemical reaction.

We tried this experiment/test together as a class. Three students made the hand warmers according to the instructions:

1 heaping tablespoon of the Water soaked Water Jelly Crystals.
1 TBSP of the iron filings to the Crystals in 3 bags.
1.5 TBSP of the calcium chloride (deicer salt).

Three students decreased the amount of iron filings to 1/2 TBSP and three students increased the amount of iron filings to 1.5 TBSP. We squished the bags all up and eagerly waited for our chemical reaction to happen. But nothing. None of the bags got warm. In fact they all remained cold. We let the bags set for 2 hours and there was no measurable heat.

Where did we go wrong? We would like to do this experiment to show the exothermic reaction and to allow this student to determine if changing the amount of iron filings will change the intensity and duration of the chemical reaction.

Any help would be greatly appreciated.

Hello,

This sounds like a fun project and I love how you are testing the variable of how much iron filings to add! What you did sounds correct to me so I'm unsure why you did not observe an exothermic reaction. To help us troubleshoot, can you tell us a bit more about the materials you are using (what brand and any label details) and if you were following a specific procedure send us a link?

Audrey