Exploring Melting Point: Turkey Timer STEM

It's time for a big Thanksgiving feast, and you are tasked with cooking the bird. How do you assure your Thanksgiving turkey has been cooked to a safe temperature, but is not overly dry? Science to the rescue! Here is a science investigation that will teach your kids or students about melting point, materials science, and product design.

If you've cooked a turkey you've probably seen a pop-up meat timer. These nifty devices are designed to pop up when the bird is done. But how does it work? This STEM investigation will answer that question and give the kids something to do while you're busy in the kitchen preparing for the feast.

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Photo by M. Rehemtulla [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

Every element of the periodic table has a melting point and a boiling point. These are the temperatures at which the element melts or boils. When elements are combined they have different melting and boiling points. Engineers put these principles to work when designing pop-up turkey timers. 

Background Information: Turkey STEM Investigation 

Here is the background information, or "spoiler", for this investigation. Depending on how open-ended you would like your student's or children's investigation to be, you can feel free to divulge this at the start, or let them make hypotheses of their own before sharing.

Inside a turkey timer is a thin piece of metal. The metal is a combination, or alloy, of lead, cadmium and bismuth. This alloy melts at a specific temperature, which is the same as a turkey needs to cook to, 180 degrees F, or 83 degrees C. When the piece of metal melts, the "pop-up" part of the timer is released.

Pop-up Turkey Timer Experiment Supply List:

• pop-up turkey timers
• water
• pan or beaker
• candy thermometer or probe thermometer
• tongs
• oven mitt or heat resistant gloves
• stove or hot plate
• a turkey! (optional for Thanksgiving day extensions)

Procedure for Melting Point Science Experiment

Using the proper safety precautions, heat some water in a pan or beaker on the stove top or hot plate. Hold the turkey timer under the water with the tongs. Insert the thermometer in the water as well. It's probably best to make this a 2 person procedure.

by Freddyz at the French language Wikipedia [GFDLor CC-BY-SA-3.0], via Wikimedia Commons

When the red part of the pop-up timer pops, record the temperature of the water. How accurate was the timer?

Try it again- to reset the timer, pull it out of the hot water and push down the red part. Allow to return to room temperature. This will solidify the alloy inside once again. To speed up the process, hold the timer closed in ice or ice water.

What do you find in subsequent trials? How consistent is the timer? Does it lose its effectiveness when it's been used more than once? Be sure to record all of your results.

Turkey Timer Experiment Extensions

• When you are cooking the bird on Thanksgiving, watch for the timer to pop. When it does, use a meat thermometer to check the temperature near where the timer is inserted into the bird. How does this compare to your experiment? 
• Engineer your own pop-up thermometer model with this lesson idea from the National Science Teacher's Association.

Looking for more Thanksgiving science? This is my go-to Thanksgiving science activity for when the kids are wild and I am a tired teacher: Thanksgiving Dinner Trophic Pyramid.

You'll find some cranberry science activities here. Check out this link if you are curious about turkey genetics. Answer the age-old question: does turkey really make you sleepy?