Download Penny Lab

Name____________________________ Hour___
Introduction:
All radioactive matter decays. Radioactive
elements become nonradioactive over time. Each radioactive
element has a unique rate of decay. This "HALF-LIFE" is the
average period of time it takes for half of the atoms in a
radioactive sample to change into new atoms. This lab will give
you a model to learn more about this concept.
Radioactive Atoms Remaining
The Half-Life of “Pennyium”
Time (sec)
Procedure:
(After reading the procedure, make a prediction of the graph on the axes above)
1. Place 100 pennies in the box provided with the head sides up. The pennies will represent
atoms of the hypothetical radioactive element “Pennyium”.
2. Cover the box and shake it (gently) for 3 seconds. This is one time interval.
3. Remove the lid and take out any pennies that are heads side down. These represent the
atoms that decayed into a nonradioactive element.
4. Record the numbers of decayed and remaining pennies (“atoms”) in your data table.
5. Repeat steps 2-4 until all of the pennies have decayed.
6. Repeat the entire experiment and record the data under trial 2.
7. Determine the average number of “atoms remaining” for your two trials.
8. Make a graph of your data plotting the average number of radioactive atoms remaining
versus time. Consider all parts of a complete graph.
Data:
Time (seconds)
0
3
6
9
12
15
18
21
24
27
30
Trial 1
Trial 2
Average
Radioactive
Radioactive
Radioactive
Atoms Decayed Atoms Remaining Atoms Decayed Atoms Remaining Atoms Remaining
Questions:
1. How long did it take for ½ of your pennies
to decay?_____________
2. What is the half-life of your pennies in
seconds?_____________
3. If you increase the amount of pennies to
200, would the overall shape of the curve
change? Explain.
4. What do you expect the half-life of
200 pennies to be?_____________
5. Given 200 pennies, how many should be left after 9 seconds?_____________
6. If the half-life of Uranium-238 is 4 billion years, how long will it take for a 100-gram
sample to decay to 50grams?
7. How many grams of a 100g sample of U-238 will remain after 2 billion years?_______
8. Given 1000 grams of Uranium-238:
a) How many grams decay after the first 4 billion years?_________
b) How many grams will decay during the second 4 billion years?________
c) How many grams will decay during the third 4 billion years? _________