Module 8
Completion requirements
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1. Module 8
1.13. Page 4
Module 8—Nuclear Decay, Energy, and the Standard Model of the Atom
Watch and Listen
Explore half-lives using this Half-Life tutorial.
Self-Check
You may check your understanding of half-lives by completing the assessment questions in the Half-life simulation.
SC 4. A student studying radioactivity makes the following measurements from a radioactive sample.
| Time (s) | Decays (Bq) |
0.0 |
100.00 |
1.0 |
75.79 |
2.0 |
57.43 |
3.0 |
43.53 |
4.0 |
32.99 |
5.0 |
25.00 |
6.0 |
18.95 |
7.0 |
14.36 |
8.0 |
10.88 |
9.0 |
8.25 |
10.0 |
6.25 |
11.0 |
4.74 |
12.0 |
3.59 |
- What is the independent variable?
- What is the dependent variable?
- Graph the information.
- What type of relationship is shown on the graph?
- From your graph what is the half life of the sample?
- After how many seconds will there be less than 1.0 Bq?
- Will the decays ever reach zero?
Check your work.
Self-Check Answers
Contact your teacher if your answers vary significantly from the answers provided here.
SC 4.
- The independent variable is the time.
- The dependent variable is the decays.
- The graphs shows an exponential relationship.
- The half-life of the sample is 2.5 seconds. It is the time when the decays reach half the original value of 100. When the decays are 50, the time is 2.5 seconds.
- After 17 seconds, there will be less than 1.0 Bq.
- No, the decays will never reach zero; but for all practical purposes, after 5 half-lives, it is difficult to accurately measure the original amount. After 10 half-lives, the original radioactive atoms are considered completely transmuted. Less than 0.01% remains.