Full Name Fatima Yaseen_______________ Block _D__
Date ____10/26/2015__
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 8 cm Decay Dish: (example)
Time (# of shake
# of decayed nuclei (#
and count events)
of corn pointing at tape)
0
0
1
Total # of undecayed
(Parent) nuclei
100
Total # of decayed
(Daughter) nuclei
0
6. Plot your values and draw a curve or best fit on a graph (see below) with the Parent nuclei
number on the vertical (y-axis) and the time (number of shakes) on the horizontal (x-axis).
7. Repeat the activity with the alternative (10cm or 5 cm) dish and plot and draw it’s curve on the
same graph using a different colour.
8. Plot the values and draw a curve or best fit on the graph with one of the Daughter nuclei using an
different color
9. Label your graph and lines clearly. ( graph and tables are on the last page)
# of Parent
Isotopes
Remaining
100%
50%
Time (# of shakes)
Questions:
1.
Generally, did the number of decay events (kernels pointing to the tape) increase, decrease, or
stay the same? Why?
As the experiment continued the kernels pointing to the tape increased because there was less
kernels moving them away from the tape.
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: around the 7th shake
b) How does your 50% compare this with the time (shakes) at which 25% remained? 25% remained after half
the amounts of shakes for 50%. (After 4 shakes which is close to 3.5)
3. Do the same comparison (above) for the 8cm tape and describe what you find.
The half like for the 8cm tape occurs at the 5th shake and the 25% occurs on the 7th which in comparison to the
5cm tape is a similar result.
4. Do you think you would you get the same results if you repeated the experiment? Explain.
No, because there are a few mistakes that I have noted, which if I were to repeat the experiment I would
definitely fix. Like as you take out a kernel you might accidently move another kernel to face the tape, without
realizing it and not being that consistent with the shake pattern.
5. What results would you expect if the tape were 3 cm long?
I would expect the experiment to take longer, and the half-life would also therefore increase.
Conclusion:
The longer your tape is the shorter the half-life is of the kernels, and if your tape is shorter it will take
longer to complete the experiment and the half-life will be longer, the curve on the graph will also be
steeper. The longer the half-life is the steeper the curve will be. There were some major errors made
during the experiment, like moving the kernels with the tweezers without noticing, perhaps some
miscounting occurred and the shaking on the kernels was also not consistent. To improve we could use
larger objects so that it is easier to see the difference and less errors can be made, as using something as
small as a popcorn kernel can be a very delicate procedure! My graph isn’t very accurate because I didn’t
draw the curve of best fit smoothly, which leads to inaccuracy. Next time I will try to draw it smoother by
printing out the graph and drawing it by hand.
Just
starting
out…
In
Progress
Getting
there
Completion/Questions
Conclusion / Reflection /
Big Ideas
0
1
2
3
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
Observations
Time (# of shake and
count events)
Got
it
# of decayed nuclei (#
of corn pointing at
tape)
0
8
2
14
Total # of undecayed
(Parent) nuclei
Total # of decayed
(Daughter) nuclei
100
92
90
86
0
8
10
14
4
5
6
7
8
9
10
11
12
Time
(# of
shake
and
count
events)
0
1
2
3
4
5
6
7
8
9
1o
11
12
13
14
27
9
9
15
5
6
3
5
7
# of decayed nuclei (#
of corn pointing at
tape)
59
50
41
26
21
15
12
7
0
Total # of undecayed
(Parent) nuclei
41
50
59
74
79
85
88
93
100
Total # of
decayed
(Daughter)
nuclei
0
21
7
8
6
7
6
4
8
7
5
6
9
4
12
100
89
82
74
68
61
55
51
43
36
31
25
16
12
0
0
11
18
26
32
39
45
49
57
64
69
75
84
88
100
5 cm tape ^^
Graph to show experiment: