Chemistry!!

1. Chemistry!! March 20, 2013 Ms. Boon

2. Objective: I can write a nuclear reaction equation and calculate the age of a sample using radioactive decay data. • Agenda: • Catalyst • Mouse trap reactor • Radioactive decay and nuclear reactions practice • Portfolio Build Catalyst • In the penny lab, each trial represented one half-life. About what fraction of the pennies were removed each trial? (In other words, what does “half-life” mean?) • Materials: Nuclear Chemistry handouts and homework

3. Video: movies file – mouse trap reactor regular and slow motion Model: Mouse Trap Reactor Video Focus Questions: • In what ways does the mouse trap reactor model simulate a nuclear chain reaction? • How is an actual nuclear chain reaction different from the mouse trap model?

4. Materials • Nuclear chemistry handouts • Nuclear energy article • Unit 11: Nuclear Chemistry – Writing Nuclear Equations • Nuclear chemistry work sheet • Homework assignments: • Due Next Class: Read pp. 658-666 Problems p. 666 #1, 2, 3, 5, 6, 7, 8 • Due Next Class: Read pp. 648-657 Problems p. 670 #34, 35 p. 671 #52, 54, 58, 60, 61, 62 • Last week: Read p. 642-643, 648-657 practice p. 653 #1-4; problems p. 657 #1, 2, 5, 6 • Last week: Read p. 658-666 Do problems: p. 666 #4, 9, 10, p. 669 #25, 26, 27

5. Quick Check: • A beta particle is a(n) • proton • Neutron • Electron • Helium nucleus

6. Quick Check: • A gamma ray can penetrate • Skin • A sheet of paper • A 2-cm thick piece of aluminum • All of the above

7. Sample Problem: Nuclear equations p. 670 #32: When a radon-222 nuclear decays, an alpha particle is emitted. Write the nuclear equation to show what happens when a radon-222 nucleus decays. 222 Rn 86 4 He + 2 218 Po 84

8. Sample Problem: Nuclear equations p. 671 #47: The radiation given off by iodine-131 in the form of beta particles is used to treat cancer of the thyroid gland. Write the nuclear equation to describe the decay of an iodine-131 nucleus. 131 I 53 0 e + -1 131 Xe 54

9. Sample Problem: Radioactive dating p. 660 #1: Assuming a half-life of 1599 y, how many years will be needed for the decay of 15/16 of a given sample. • What is the question asking? • # years for 15/16 of a sample to undergo radioactive decay • How many half-lives must pass to decay 15/16 of a sample? • Use the half-life pattern: • 1 → ½ → ¼ → 1/8 → 1/16 → 1/32 → 1/64 • This pattern shows how much of an original sample is left after each half-life. • For 15/16 to decay, 4 half-lives pass • 1599 y x 4 = 6396 y

10. Sample: Radioactive dating p. 662 #1: The half-life of polonium-210 is 138.4 days. How many mg of polonium-210 remain after 415.2 days if you start with 2.0 mg of the isotope? • What is the question asking? • How much Po is left after 415.2 days • How many half-lives passed in 415.2 days? • Divide: time/half-life • 415.2 d/ 138.4 d = 3 half-lives • Use the half-life pattern to determine the fraction of the sample left over: 1 → ½ → ¼ → 1/8 • Multiply the fraction by the original mass: • 1/8 x 2.0 mg = ¼ mg or 0.25 mg

11. Practice • Complete All Nuclear chemistry handouts • Nuclear energy article • Unit 11: Nuclear Chemistry – Writing Nuclear Equations • Nuclear chemistry work sheet • Homework assignments: • Due Next Class: Read pp. 658-666 Problems p. 666 #1, 2, 3, 5, 6, 7, 8 • Due Next Class: Read pp. 648-657 Problems p. 670 #34, 35 p. 671 #52, 54, 58, 60, 61, 62 • Last week: Read p. 642-643, 648-657 practice p. 653 #1-4; problems p. 657 #1, 2, 5, 6 • Last week: Read p. 658-666 Do problems: p. 666 #4, 9, 10, p. 669 #25, 26, 27

12. Announcements • Grades: • You may pick up your benchmark grade report at student led conferences. • Make up work: • Make up assignments are posted on the board. • Tutoring: • Tutoring is Friday at 3:45. • Worksheets and study guides: • Do not throw away any Semester 2 materials. You need these to study for the CST.