The Candyville Mall Dilemma
Students Name(s):____________________________________________________
Storyline:
Attention Candyville Citizens,
As many of you already know, we have been working to build our new mall.
Unfortunately, we have had to postpone building. While we were digging at the excavation site,
we found a large fossil. The city will not allow us to continue building the mall until we have
figured out how old the fossil is. Due to the upheaval of the Earth during excavation we are
unable to use the Law of Superposition to age the fossil. Fortunately, the fossil contains
M&Mium which is a radioactive element scientists say can help us date the fossil. Our mayor is
offering a reward for any citizen who is able to assist in telling us the age of this fossil.
N. Desperation
Mall Contractor
Overview & Directions:
Radioactive Decay is when atoms of one element are changed into atoms of another
element. Weird! M&Mium is one of those radioactive elements. When you see an M&M with
the white “m” facing up, it is original M&Mium and still radioactive. When you see an M&M
with the white “m” facing down, it is the changed M&Mium and no longer radioactive.
In the first part of this activity you will be keeping a data table of the radioactive decay
of M&Ms. After you have fully filled the table, you will graph your data and determine the halflife of M&Ms.
In the second part of this activity you will use your calculated half-life from part 1 to
determine the age of the fossil that was found at the mall excavation site.
Part 1:
Gather your materials from your teacher (100 M&Ms in a Container) and go to your work
station. Read the directions below for part 1 of this activity:
1. Shake M&Ms in Container
2. Empty M&Ms out onto table
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The Candyville Mall Dilemma
Students Name(s):____________________________________________________
3. Separate M&Ms with M facing up (Radioactive M&Mium) from M&Ms with M down
(Changed M&Mium).
Changed M&Mium
Radioactive M&Mium
4. Record the number of Radioactive M&Mium in the data table below.
5. Set aside the Changed M&Mium (M down). Return the Radioactive M&Mium(M up) to the
container and repeat directions 1-5 until no Radioactive M&Mium Remain.
Data Table:
Times Emptied on the
Table (Each time is
representative of 1 Million
Years)
0
1
2
3
4
5
6
7
8
9
10
# of Radioactive M&Mium Remaining
(M&Ms with “M” showing)
100
58
26
18
10
7
3
1
0
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The Candyville Mall Dilemma
Students Name(s):____________________________________________________
Use your data table from the previous page to create a graph below.
Post-Lab Questions:
Part 1- Graph Analysis
1. The term half-life means the amount of time that has to pass in order for half of your
radioactive material to be changed. Look at your graph and determine how many millions of
years had to pass for you to go from your original 100 M&Mium to 50 M&Mium remaining.
Half-Life of M&Mium: Responses vary due to experimental data. Ideally, students should
respond with an answer close to the value of 1. With the data found in this key, the answer
would be close to 1.2 Million Years.
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The Candyville Mall Dilemma
Students Name(s):____________________________________________________
Part 2- Apply What You Know
Now you will use your graph of the Radioactive Decay of M&Mium to determine the age of the
fossil that was found at the mall excavation site.
2.a. Assume that the fossil pictured on the
left started with 100 M&Ms. Count the # of
M&Mium you see. Use your graph of the
decay of M&Mium from part 1 to figure out
how old the fossil is.
Age of T-Rex Fossil Containing M&Mium:
Answers will vary depending on student
graphs, but the answer should be between
4 and 10 Million Years. According to the
graph in this key, the answer would be close
to 5 Million Years.
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The Candyville Mall Dilemma
Students Name(s):____________________________________________________
2.b. Assume that the fossil pictured above started with 100 M&Ms. Count the # of M&Mium
you see. Use your graph of the decay of M&Mium from part 1 to figure out how old this fossil
is.
Age of Pterodactyl Fossil Containing M&Mium: Answers will vary depending on student graphs,
but the answer should be between 4 and 10 Million Years. According to the graph in this key,
the answer would be close to 5 Million Years.
Which fossil is older (T-Rex or Pterodactyl)? The Pterodactyl would be the older fossil. The
fossils, both started with the same amount of M&Mium, but the Pterodactyl fossil has less in
the photograph. The Pterodactyl fossil has decayed more and is older than the T-Rex.
© Copyright 2014- all rights reserved www.cpalms.org
The Candyville Mall Dilemma
Students Name(s):____________________________________________________
Part 3- What Do You Think?
3. Why would scientists use the method you used in this activity (radioactive dating) as opposed
to the superposition method of dating to determine the age of the Candyville Mall Fossil?
Responses may vary but should include an argument based on the initial letter written by the
contractor. Teacher may use rubric for the question 3 response (found in teacher guide
attachment).
Sample Responses:
CompleteScientists would use the radioactive dating method as opposed to the superposition method
because the ground where the fossil was found was disturbed in the building process that
happened at the excavation site. In order to use superposition, you date the fossil based on
relative rocks around it. In order to date it radioactively, all you need is to know the half-life or
radioactive decay of an element that is contained in the item you are attempting to date.
PartialScientists should always use radioactive dating because it doesn’t depend on the materials
found around the fossil, only the fossil itself.
IncompleteMy teacher is awesome. I really liked eating all their candy and not working on the lab!
Rubric:
Incomplete- 0
The student has not
attempted to answer the
question or the answer is
completely unrelated to the
question topic.
Partial- 1
The student attempted to
answer the question and has
supplied relevant information,
but the response does not
include information from the
original letter sent by the mall
contractor.
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Complete- 2
The student has supplied
relevant information and
cited information from the
letter sent by the mall
contractor to support their
argument for why they would
choose one method over
another.