Science project

Radioactive Decay!

In this science project, each coin represents an atom. A coin has a 50 percent chance of showing heads, so in any round we would expect approximately half the coins to show heads. This corresponds to the decay of half the atoms in a radioactive substance and therefore the coins are indeed a good model.  On a process level, the student will be using the scientific method to test and observe the pattern of the coin sample and extrapolate the” half life “of the coin sample from the obtained data. Hopefully, the result is a clear- cut operational concept of the half- life of radioactive substances.


  • 100 pennies
  • pen
  • paper
  • a bag to hold the coins

Experimental Procedure:

  1. Gather all the materials you will need for this project. These include 100 coins, pen, paper and a strong paper or plastic bag for your coins. You may wish to include a camera and take photos of the steps as you go though the experiment.
  2. Copy the Data Chart provided below so that you can readily record your observations.
  3. Put the coins in the bag. Close the bag securely and shake the bag.
  4. Now spill the coins out on the table in front of you. Do not lose any! You may want to snap a photo.
  5. Gather and count all the coins that are heads. Put them aside. In the Data Chart record this number of coins in the column Coins Removed. Now subtract and calculate the number remaining and put that number in the Coins Remaining column.
  6. Now collect the coin that were tails and put them back in the bag .Close the bag and shake!
  7. Repeat steps 4,5 and 6 until you have run out of coins to put back in the bag
  8. Now take the data you have and draw a bar graph showing what happened to the size of your coin sample as went through all of the steps.
  9. Review all of your data. Write up your report by responding to the following questions: Explain what each coin represents. Note how many times you had to toss the coins before they were all used up. Did you find a pattern? What does the bar graph show?
  10. Think about it! If you repeated this experiment again, do you think you would get the same or different results? Why?
  11. Explain why this experiment was useful in replicating a model of radioactive decay.  Why were the coins a good way to model half-lives? Would the model work as well if we used 1000 coins? At what point should we be concerned with transmutation?

Data Chart


# of Coins Removed

# of Coins Remaining
































Terms/Concepts: radiation; nuclear medicine; isotopes; radioactive decay;  decay rate; half-life; carbon 14 dating; transmutation


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Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state's handbook of Science Safety.

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