With crisper temperatures, hand warmers start popping up on dollar tables at the stores. These inexpensive ones come two to a cellophane package, one for each hand. The warming chemical is inside a non-woven bag. Here’s an experiment that gives children a chance to explore the hand warmer reaction and learn more about the chemical reaction of iron with the air and energy.
Safety note: Be sure to explain safety precautions to children. This experiment uses iron. Skin protection should be used. Avoid getting chemicals from the hand warmer on skin, eyes, or clothing. After this experiment dispose of iron in garbage. Disclaimer: All information provided on this site is for entertainment and education purposes only. Using any information from thecasabouquet.com is at your own risk.
This post contains affiliate links: if you make a purchase using these links, I’ll receive a small compensation towards maintaining this blog, at no extra cost to you.
If possible, a few days or more in advance, carefully cut open one hand warmer bag and empty the iron filings into a sandwich or freezer reclosable storage bag. Put the open bag in a safe place and allow air to react with the iron. You may want to stir the iron around a bit every time it cools off to allow more surfaces to react with air. Seal up the bag before using it with children.
- Ask the children to read the information on the package and note the contents, safety precautions, and average temperature.
- Carefully open the outer package and remove one hand warmer. Shake or gently squish the pack and take note of observations.
- Very carefully, cut open the warmer pack and pour the iron into an empty reclosable plastic bag. Measure and record the temperature of the iron. Feel the bag with your hands also.
- Leave the bag open for a few minutes. Record the number of minutes and take the temperature.
- Close the bag. After the same number of minutes take the temperature again. Feel the bag with your hands and record observations.
- If you have an old packet that has already reacted, perform the same experiment with it. Compare the results to the newly opened packet.
What is the energy change? What is the chemical reaction of the iron? Is there a difference between “new” iron and the packet of material that has already reacted? Where in every day life have you seen iron and iron oxide? What would be the difference in energy if the iron was in a solid block? How much extra surface area is available because of the iron being in filings? Was this reaction endothermic or exothermic? What other experiments could be done? Can you make a design for hand warmers that uses a simple chemical reaction?
- Iron powder hand warmers
- Reclosable plastic bags, 2
- Safety glasses
- thermometer or Vernier LabQuest with Vernier temperature probe
- paper or notebook for recording results, pen
What is the science?
Content: thermal energy, chemical reaction, endothermic, exothermic
Iron reacts with humid air to make a new compound, iron oxide or iron hydroxide. The formation of the new compound releases energy into the surroundings, which we feel as heat in the hand warmer reaction. By using iron filings in the hand warmer, the exposed sides react. The hand warmer can be “recharged” by shaking or massaging the packet in air, exposing more “sides” to the air to react.
- The chemistry of rust from Corrosion Doctors
- Hand warmers from PBS Rough Science
- General Lab Safety resources from Flinn Scientific. Be sure to check out the Student Safety Contract.
- LabQuest2 from Vernier Software & Technology
Sometimes in STEM we get carried away with procedure and making sure we take all the measurements and then analyze. It is good to take a moment and let the children actually feel the temperature change of the hand warmer reaction with their hands. It takes the energy transformation out of the totally abstract to something they can remember. There will be many children who have never used hand warmers and might want to discuss who needs these and why they are useful.
I’ll be looking for comments below, or contact me at lisa [at] thecasabouquet[dot]com.