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Problem: What is the relationship between the amount of radioactive decay and the time allowed for decay?


Materials: 100 die, graph paper,


Procedure: the 100 die represent 100 radioactive iodine-124 atoms. Place the 100 die into a paper bag and shake them up. Shake them out of the bag. Each die showing a number 1 face up represents an atom that has decayed. Remove all the atoms that decayed for the first toss (day one). Put the rest of the die back in the paper bag and shake them up again. Repeat the process for the second toss (representing day 2).




Complete the following table:


Time (days) Atoms remaining


0 100

1 ___

2 ___

3 ___


Continue till all atoms have decayed. This may take approximately 25 steps.


A) How long did it take for half the atoms to decay from 100 to approximately 50?

B) How long did it take for the atoms to decay half again (from about 50 to about 25?

C) How long did it take for the atoms to decay half again?

D) What is the average of the values in A , B and C?


If the equation of your data is approximately:


y = 100(0.83x)




1) What are the independent and dependent variables?

2) How are the variables changing with relationship to each other?

3) What happens to the dependent variable when the independent variable increases? decreases?

4) How does the relationship shown in this experiment compare with other relationships you have so far seen?

5) How does the equation for this relationship compare with those of other equations you have studied?

6) What is the meaning of half-life in a radioactive substance?

7) What is the approximate half-life of your experiment?




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