Teaching chemistry in middle school is difficult. You can’t see atoms and you can’t feel electrons moving around.The material leans toward the abstract, even though atoms are what make up all concrete objects! To make it worse, this unit comes during the mid-winter, still not close enough to spring break time of year.

I always try to use hands-on simulations or interactive labs to help students connect to the information. (For example, these cereal Bohr model projects). Radioactive elements are another great one to simulate (I mean, you have to simulate it… highly radioactive elements are frowned upon at school). Radioactive Pennies a mini lab that can bring the concept to life. This lab uses probability and flipping coins to simulate what happens to elements that undergo radioactivity. Each round represents a half-life of the penny element. So after discussing what happens when an element becomes radioactive, students participate in this!

Materials Needed:

  • 50 pennies per group
  • Ziploc or paper bag
  • Blank graph

Instructions for Radioactive Pennies

  1. Students put all the pennies into the bag, shake, then dump them out onto the table
  2. Any pennies that land on heads are the ones that have changed elements. Put these in a pile to the side.
  3. Place all the tails back into the bag to be dumped again
  4. Repeat the process until all the “element” has changed
  5. Students record how many pennies landed heads after each round and create a line graph plotting the number of heads each time on the y-axis and rounds on the x-axis.

    This shows how many pennies were heads after each round

Comparison to a half-life of an element

Students should notice a pattern of about half the pennies being flipped to heads each round. Of course, it is not always half, but this idea is the same as an element’s half-life. It takes each element a certain amount of time to fall to half its size. It takes one round for the group of pennies to fall to half its size. From this, you can predict about how long it would take for all the pennies to flip, just as scientists can predict about how long it takes for certain elements to “fall apart.”


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