Radioactive Decay Curve

Alan L. Tobecksen              Henry Clay Elementary School
                               13231 Burley
                               Chicago Il 60633
                               (312)535-5600

Objectives:

Parts of this experiment are suitable for first grade through sixth grade but 
the intended grade level is seventh through high school.

1. Students will learn to gather and organize data.
2. Students will practice graphing simple data.
3. Students will observe an exponential curve.
4. Students will learn that the points where the quantity becomes one-half as 
   much occurs at regular intervals.

Materials Needed:

Each group of 2 to 4 students will need
30 pairs of dice (60 di)
a container large enough to hold the dice
graph paper

Strategy:

Each group rolls the 60 di all at once.  The team removes all di that turn up as 
either a 5 or a 6.  Count the remaining di.  Record this information. Gather up 
the remaining di and roll them again.  Continue doing the rolls until there is 
only 1 di left or 10 rounds have been completed.  Students then graph number of 
roll verses number of dice left. 

Performance Assessment:

Subjective: The teacher should observe the students to be sure that the exercise 
is being done correctly and that data is being gathered and organized.
Objective: The data table and graph can be given a grade.

Conclusions:

Students sometimes have confusion understanding the directions - it is easier to 
give a short demonstration of what is to be done.  Each group usually has an 
almost perfect result and if all data from all groups is gathered and averaged, 
a perfect result is guaranteed.  The results of remaining di follow this pattern 
usually very closely - 40 left on the first roll, 27 left on the second roll, 18 
left on the third roll, 12 left on the fourth roll, 8 left on the fifth roll, 5 
left on the sixth roll, 4 left on the seventh roll, 3 left on the eight roll, 2 
left on the ninth roll, 1 left on the tenth roll.
The students love rolling the dice.

References:

Merrill Physics - Teacher Guide