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# Half lives

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##### Description:

Students will explain the process of half-life as it relates to radioactive decay. They will also perform simple half-life calculations.

Here are your notes. Keep in mind these are just the basics.

(more)

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Tutorial

## Nuclear Theory Part 2: Half-lives

What is half-life and how do you calculate it?

Source: various educators and Langhans

## Half-lives: These are the “S” in WSQ. You must have them under your video notes completed by the due date on the Unit Plan.

1. Fluorine-20 has a half life of 11.6 seconds. If you started with 100 grams of the sample of F-20, how much would remain after 11.6 seconds?            After 23.2 seconds?

2. Strontium-90 has a half life of 28 days.  If you started with 200 grams of the sample of Sr-90, how much would remain after 56 days?

3. C-14 has a half-life of 5730 years.  If a bone originally had a mass of 1000 grams of C-14, how much would remain after 5730 years?

4. Iron-59 has a half-life of 45 days.  If the original sample of Fe-59 had a mass of 2000 grams, how much would remain

a. after 45 days?
b. After 90 days?
c. After 135 days?
d. After 180 days?

5. After 1 half-life, what fraction of the sample remains?                      How much is decayed?

6. After 2 half-life, what fraction of the sample remains?                      How much is decayed?

7. After 3 half-life, what fraction of the sample remains?                      How much is decayed?

8. After 4 half-life, what fraction of the sample remains?                      How much is decayed?

9. After 5 half-life, what fraction of the sample remains?                      How much is decayed?

10. If I find a 100-g bone that I know is 11460 years old and the half-life of C-14 is 5730, what was the original mass of the bone?

Source: Langhans and various educators

## Question- asking Higher Order Thinking (HOT) questions; use the following as your guide:

1. A question that you are still confused about (be specific, include which part of the video, etc)
2. A question that connects the videos together (i.e. asking about the relationship between the content)
3. A question you think you know the answer to, but you want to challenge your classmates with
Use your Unit Plan to help with question starters

Source: inspired by C. Kirch