Full Name ____Daniel Menzies________ Block _C_ Date ____Oct. 26__________________
Half Life Popcorn Lab
Purpose: To simulate radioactive decay and determine the half-life of a radioactive substance.
Procedure
1.
2.
3.
4.
Count out 100 kernels of popcorn
Put the kernels into the petri dish with a 5cm or 10cm piece of masking tape attached
Copy a table like the one below into your notebook.
Shake the petri dish and observe the kernels. Count how many kernels point to the tape and
record this value in the table below.
5. Remove the number of kernels that were pointing to the tape and repeat. Continue to record you
decay values and remaining nuclei in your table until all the kernels have decayed.
Results for 8cm Decay Dish:
Time (# of shake
# of decayed nuclei (# of
and count events)
corn pointing at tape)
0
0
1
17
2
18
3
20
4
8
5
6
6
7
7
7
8
6
9
8
10
1
11
2
Results for 5cm Decay Dish:
Time (# of shake
# of decayed nuclei (# of
and count events)
corn pointing at tape)
0
0
1
14
2
15
3
16
4
13
5
9
6
6
7
7
8
7
9
5
10
3
11
3
12
2
Total # of undecayed
(Parent) nuclei
100
83
65
45
37
31
24
17
11
3
2
0
Total # of decayed
(Daughter) nuclei
0
17
35
55
63
69
76
83
89
97
98
100
Total # of undecayed
(Parent) nuclei
100
86
71
55
42
33
27
20
13
8
5
2
0
Total # of decayed
(Daughter) nuclei
0
14
28
45
58
67
73
80
87
92
95
98
100
6. Plot your values and draw a curve or best fit on a graph (see below) with the Parent nuclei
7. number on the vertical (y-axis) and the time (number of shakes) on the horizontal (x-axis).
8. Repeat the activity with the alternative (8cm or 5 cm) dish and plot and draw it’s curve on the
same graph using a different colour.
9. Plot the values and draw a curve or best fit on the graph with one of the Daughter nuclei using an
different color
10. Label your graph and lines clearly.
120
100
80
Parent 8 cm tape
60
Parent 5 cm tape
# Isotopes
Remaining
Daughter 5 cm tape
40
20
0
1
2
3
4
5
6
7
8
9
10
11
12
13
Time (# of shakes)
Questions:
1.
Generally, did the number of decay events (kernels pointing to the tape) increase, decrease, or
stay the same? Why? ___ They decreased because the overall number of of kernels diminished.
There were less odds for the kernels to point to the tape because their were less kernels total. __
2. a) Use your graph to determine the time (number of shakes) at which the number of remaining nuclei was half
(i.e. 50) for the 5cm dish. (This represents the half-life.) Half –life: _4 shakes _
b) How does your 50% compare this with the time (shakes) at which 25% remained? ___It took less time for a
half life to happen (50%) then two half lives (25%)__
3. Do the same comparison (above) for the 8cm tape and describe what you find.
___It was about the same, just took a bit longer.___
4. Do you think you would you get the same results if you repeated the experiment? Explain.
__No I do not think so because the laws of probability almost say that the 5 cm tape dish experiment should
have been a lot slower and taken more time then the 8cm tape dish. It just so happened that all the numbers
were almost the same ___
5. What results would you expect if the tape were 3 cm long?
__It would most likely take a few more shakes because there are less odds of the kernels landing facing a
smaller point .__
Conclusion:
__I believe that this experiment both did and did not represent half life decay. I do belive it supported the idea
of half life decay because the amount of kernels accurately resembled the amount of parent cell because less
and less were taken away but the total number of those taken away was getting bigger. I do not believe it
represented the experiment very well because I think the amount of kernels getting taken away with the 8cm
and 5 cm tape were to similar. I think it would have been more accurate if less kernels landed on the five cm
tape. Perhaps that is what radioactivity is, that it is just luck sometimes, that nature just causes random odds to
lean an experiment in one sides favor. So in conclusion I liked the premise of the experiment and I enjoyed
how it taught me the rules of half life decay but I didn’t like the fact that the odds changed in such a way that it
was really close.__
Just
starting
out…
In
Progress
Getting
there
Observations
+
Completion/Questions
+
Conclusion / Reflection /
Big Ideas
Got
it
+
Rock Star
 Table accurately completed and filled
out
 Graph accurately drawn and labelled
 Graph includes the parent and
daughter isotope remaining
 Questions have been accurately
answered
 Answers demonstrate a good
understanding of the concepts
 Thoughtful/meaningful answers
 No questions have been left blank
 Student shows exceptional ability to
sum up the big ideas of the lab
activity
 Student can describe the purpose
and specifically report his/her findings
 Detailed yet concise
 Student has demonstrated reflection
on the activity, addresses possible
errors made during lab activity and
improvements for future tests