DVD 1 Bmk 5, 34

1. 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. 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…. . DVD 1 Bmk 5, 34

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

5. Q1 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? 5.715 years old C A 4715 years old 6715 years old B not enough information D D Answer End

6. 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? Q2 5.715 years old C A 4715 years old 6715 years old B not enough information D D Answer End

7. 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? Q3 Clue C 17145 years old C Working 22860 years old A End 8 years B not enough information D Answer

8. 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? Q4 Clue Working C 17145 years old 22860 years old A A End 16 years old B not enough information D Answer

9. 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? Q5 Working C 710000 counts per second Clue 8000 counts per second B B End 250 counts per second A not enough information D Answer

10. Q6 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 17145 years C C Clue 28575 years A End 28.575 x 103 years D not enough information B Answer

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

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

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

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

15. Clue for Q5 . 6 x 5715 years → 125 counts per s 5 x 5715 years → ? counts per s Return

16. 6 x 5715 years → 125 counts per s 5 x 5715 years → 250 counts per s 4 x 5715 years → 500 counts per s 3 x 5715 years → 1000counts per s 2 x 5715 years → 2000 counts per s 1 x 5715 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. Clue for Q6 0 years → 72 mg Return

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