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DVD 1 Bmk 5, 34

1. Half life and QuestionsNotes for teachers using this resource…

This set of slides is part of a series Half Life and includes:1. Introduction to Radioactivity2. Carbon in Life and Death3. Carbon Dating4. 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….

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.

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

?

?

1 half life

?

?

A

B

5.715 years old

4715 years old

6715 years old

C

EndD 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?

A

B

5.715 years old

4715 years old

6715 years old

C

EndD 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?

AB

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

AB

17145 years old

22860 years old

16 years old

C

End

D not enough information Answer

Q4After 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

BA

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?

WorkingClue

A

D

17145 years

28575 years

28.575 x 103 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?

WorkingClue

0 years → 1000 counts per s5715 years → ? counts per s

Return

Clue for Q3

0 years → 1000 counts per s5715 years → 500 counts per s

2 x 5715 years → 250 counts per s 3 x 5715 years → 125 counts per s

Next Question

0 years → 10000 counts per s

Return

Clue for Q4

0 years → 10000 counts per s5715 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

.

6 x 5715 years → 125 counts per s5 x 5715 years → ? counts per s

Return

Clue for Q5

.

6 x 5715 years → 125 counts per s5 x 5715 years → 250 counts per s4 x 5715 years → 500 counts per s3 x 5715 years → 1000counts per s2 x 5715 years → 2000 counts per s1 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

0 years → 72 mg

Return

Clue for Q6

0 years → 72 mg5715 years → 36 mg

2 x 5715 years → 18 mg 3 x 5715 years → 9 mg

No more questions!