Name:
Date:
Period:
Coinium Dating Lab (50 pts)
Background:
• One of the tools available to scientists who study ancient climates is called carbon14 dating
• This method can determine the age of objects
• Today, you are going to experience something similar to carbon-14 decay, coinium
decay and see if it occurs in a predictable way!
Purpose:
• To explore how radioactive isotopes decay and see if it occurs in a predictable way.
Materials:
• Containers
• Pennies
• Graph paper
• Clock or stop watch
• Colored pencils and rulers
Pre-lab Questions (10pts):
1. Are all isotopes radioactive? What makes an isotope radioactive?
2. Do you think radioactive isotopes decay in a predictable way? Why or why not?
3. What are the names and symbols of the three types of radioactive decay we are
studying in class?
4. Is all radioactive decay dangerous? Give an example of decay that is dangerous and if
you answered no, an example of not dangerous decay.
5. Describe one use of radiochemical dating that we have not talked about in class.
Procedure:
1. Place 50 atoms (pennies) into a container
2. Shake container for 10 seconds
3. Gently pour pennies onto the lab table and separate out the decayed atoms
(represented by “tails up”)
4. Count the number of undecayed atoms (represented by “heads up”)
5. Enter the number of decayed and undecayed atoms into Table 1.
6. Repeat steps 2-5 until all the atoms have decayed (or you have one coin left)
7. Create a line graph* to represent your data in Figure 1. (# atoms vs. time)
8. Repeat the experiment again, this time choose an amount of pennies between 25 and
100, and a time frame between 5 and 30 seconds.
9. Write your choice on the board, no other lab group may do the same combination
10. Enter you data into Table 2
11. Create a line graph* to represent your data in Table 2
12. Post Graph #2 up in the classroom and compare your results to the other lab groups
13. Calculate the theoretical half-life values and graph it in a different color on your first
graph. The theoretical values are based on the assumption that heads up and tails up
are equally probable – for example, the theoretical value is 25 after the first run.
*Graphing notes:
• Quick reminder that the X- axis is the independent variable and the Y-axis is the
dependent variable
• Be sure to label each axis and draw a best fit line!
Data Table 1: 50 atoms and 10 seconds
Half
Time Undecayed Decayed
Life
(sec)
Atoms
Atoms
“heads”
“tails”
1
0
Table 2: ____ atoms and ____ seconds
Half
Time Undecayed Decayed
Life
(sec)
Atoms
Atoms
“heads”
“tails”
1
2
10
2
3
20
3
4
30
4
5
40
5
6
50
6
7
60
7
8
70
8
9
80
9
10
90
10
11
100
11
12
110
12
13
120
13
14
130
14
15
140
15
Theoretical Value
Run
1
Undecayed
2
3
4
5
6
7
8
9
Concluding Questions (20pts)
1. Define the term half-life:
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2. What does it mean when we say an atom has “decayed”?
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3. For Table 2, at the end of each half-life, at approximately what percentage are the
atoms decaying? ___________________________________________________
4. Compare Graph # 1 to Graph # 2. Give at least 3 examples of how they are similar and
3 examples of how they are different.
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5. Compare your Graph # 2 to Graph #3 or the theoretical half-life values. Do you notice
any patterns or trends? Explain using the terms: half-life, decay, undecayed, atoms, and
time.
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6. Does the amount of time you shake affect the outcome? _______ Does the number of
atoms you start with affect the outcome? ________________________
Explain:________________________________________________________________
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7. How do scientists use radioactive decay to date fossils and artifacts?
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