1. . DVD 1 Bmk 5, 34 1. Half life and Questions Notes for teachers using this resource… This set of slides is part of a series Half Life and includes: 1. Introduction to Radioactivity 2. Carbon in Life and Death 3. Carbon Dating 4. Questions on Half Life It is interactive, using the idea that students have cards A,B,C,D,E which they can raise in response to the multiple questions – contact me at de@nelcollege.school.nz for more on this method of teaching.de@nelcollege.school.nz The buttons DVD …. (as the one below) are simply a reminder to me to play DVD clips that I have as a resource. There are some links to alter….

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3. . How old is a piece of wood three half lives of C-14 since the time the tree died? 1 half life ? ? Half life of C14 = 5730 years 1 half life ? ? ? ?

5. A B 5.715 years old 4715 years old 6715 years old C End D not enough information Answer Q1 D After a tree dies, it no longer absorbs C-14 from the atmosphere. The C-14 in it starts to decay. The half life of the isotope C -14 is 5715 years. A sample of a fossil tree has 1000 nuclei of C-14. How long ago did the tree die?

6. A B 5.715 years old 4715 years old 6715 years old C End D not enough information Answer Q2 D After a tree dies, it no longer absorbs C-14 from the atmosphere. The C-14 in it starts to decay. The half life of the isotope C -14 is 5715 years. A sample of a fossil tree gives a radioactivity count of 1000 counts per second. How long ago did the tree die?

7. A B 17145 years old 22860 years old 8 years C End D not enough information Answer Q3 C When a tree dies, it no longer absorbs C-14 from the atmosphere. The C-14 in it starts to decay. The half life of the isotope C -14 is 5715 years. A sample of fossil tree gives a radioactivity count of 125 counts per second. The moment the tree died its radioactivity count was 1000 counts per second. How long ago did the tree die? Working Clue

8. A B 17145 years old 22860 years old 16 years old C End D not enough information Answer Q4 After a tree dies, it no longer absorbs C-14 from the atmosphere. The C-14 in it starts to decay. The half life of the isotope C -14 is 5715 years. A sample of fossil tree gives a radioactivity count of 625 counts per second. The moment the tree died its radioactivity count was 10000 counts per second. How long ago did the tree die? A Working Clue

9. B A 710000 counts per second 8000 counts per second 250 counts per second C End D not enough information Answer Q5 B When a tree dies, it no longer absorbs C-14 from the atmosphere. The C-14 in it starts to decay. The half life of the isotope C -14 is 5715 years. A sample of fossil tree gives a radioactivity count of 125 counts per second. The tree died 34290 years ago. What was its radioactivity count the moment the tree died? Working Clue

10. A D 17145 years 28575 years 28.575 x 10 3 years C End B not enough information Answer Q6 C When a tree dies, it no longer absorbs C-14 from the atmosphere. The C-14 in it starts to decay. The half life of the isotope C -14 is 5715 years. A sample of fossil tree has 9 mg of C-14. The same sample had 72mg of C-14 when the tree died. How long ago did the tree die? Working Clue

11. 0 years→ 1000 counts per s 5715 years→ ? counts per s Return Clue for Q3

12. 0 years→ 1000 counts per s 5715 years→ 500 counts per s 2 x5715 years→ 250 counts per s 3 x5715 years→ 125 counts per s Next Question

13. 0 years→ 10000 counts per s Return Clue for Q4

14. 0 years→ 10000 counts per s 5715 years→ 5000 counts per s 2 x5715 years→ 2500 counts per s 3 x5715 years→ 1250 counts per s 4 x5715 years→ 625 counts per s Next Question

15. . 6 x5715 years→ 125 counts per s 5 x5715 years→ ? counts per s Return Clue for Q5

16. . 6 x5715 years→ 125 counts per s 5 x5715 years→ 250 counts per s 4 x5715 years→ 500 counts per s 3 x5715 years→ 1000counts per s 2 x5715 years→ 2000 counts per s 1 x5715 years→ 4000 counts per s 0 years→ 8000 counts per s 34290 years→ 34290/5715 half lives 34290 years→ 6 half lives Next Question

17. 0 years→ 72 mg Return Clue for Q6

18. 0 years→ 72 mg 5715 years→ 36 mg 2 x5715 years→ 18 mg 3 x5715 years→ 9 mg No more questions!