Earth Science assignment

Half Life Modeling Activity

Learning Goal:  Construct a decay curve for a hypothetical radioactive isotope which has a half life of 2 minutes.  Practice with the concepts involved in radiometric dating.

1. Cut out 100 .5x .5 inch squares out of printer paper. (you can use random.org coin flipper to model this if you don't want to use paper)
2. On one side write H and the other write T on each piece.
3. Drop the 100 pieces from eye level and allow them to fall to the floor.
4. Count the number of heads and tails.
5. H represents parent isotope atoms and T represents daughter atoms.
6. Repeat the above procedure but only drop the  parent isotopes.  Remove the daughter atoms.
7. Construct a decay curve for this isotope.  On the Y axis plot number of parent atoms remaining.  On the x axis plot the number of half lives.
8. Each time you do a drop represents a half life.
9. Complete each drop every two minutes.
10. Repeat the procedure until you have no more parent isotopes remaining.
11. How long did it take for all of your parent isotopes to decay?
12. How many half lives took place?
13. How old would a fossil be after the 4th half life according to your graph?
14. What questions do you still have about radiometric dating?
15. What was the ratio of parent to daughter atoms for each half life?
16. Use your graph to find the age of the sample when 30 parent atoms remain.