Grade 10 · Science · Chemistry

10th grade Half-life: how much is left worksheet

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Half-life: how much is left

Grade 10 Science Worksheet - Challenge Me

NameDate

Circle the best answer, or write your answer on the line.

A wooden object has 25% of the carbon-14 found in living wood. Using a half-life of 5,730 years, about how old is it, Ari?
A wooden object has 12.5% of the carbon-14 found in living wood. Using a half-life of 5,730 years, about how old is it, Bo?
3.
Ancient scrolls found near Qumran give 10.8 counts per minute per gram of carbon; living carbon gives 13.6. About how old are they, Jun?
- About 19,000 years
- About 5,730 years
- About 1,900 years
4.
A tracer's count falls from 80 to 10 per minute in 24 hours. What is its half-life, Kira?
- 12 hours
- 3 hours
- 8 hours
5.
Hospitals make technetium-99m (6.01 h) on site from molybdenum-99 (66 h). Why, Luz?
- It decays too fast to ship far
- It lasts too long to store
- Molybdenum-99 is stable
6.
Milo says nothing is left after two half-lives, since two halves make a whole. Agree or disagree?
- Agree: half-lives add to 100%
- Agree: two halves make the whole
- Disagree: a quarter is left
7.
Pia says each nucleus waits exactly one half-life and then decays. Agree or disagree?
- Disagree: it describes a large group
- Agree: they decay together
- Agree: each one has a timer
8.
Which has more left after one day: technetium-99m (6.01 hours) or iodine-131 (8.02 days), Ren?
- Technetium-99m
- Iodine-131
- They have the same left
9.
Fluorine-18, used in PET scans, has a half-life of 110 minutes. What fraction is left after 220 minutes, Tala?
- 0
- 1/4
- 1/2
10.
Which isotope has the longest half-life, Zee?
- Fluorine-18
- Iodine-131
- Carbon-14

Half-life: how much is left. Every version has 10 questions, and the answer key prints on the second page.

I can say a half-life is the time for half of a sample to decay, and that (1/2)ⁿ remains after n half-lives.
I can find the amount left, the half-life from data, and the time to reach a fraction.
I can date once-living things with carbon-14 (5,730 years) and say its limits.
I can say why short half-lives suit medical tracers.

Standard: supports HS-ESS1-5, HS-ESS1-6

half-life: Time for half of a radioactive sample to decay

decay: A nucleus changing and giving off radiation

carbon-14 dating: Finding age from the carbon-14 left in once-living material

tracer: A small amount of a radioactive isotope followed by a detector

activity: Decays per minute, measured by counts

Your child treated decay as losing the same amount each time. Each half-life halves what is left, so the amount shrinks by (1/2)ⁿ.

What is the most common mistake with half-life: how much is left?

Your child treated decay as losing the same amount each time. Each half-life halves what is left, so the amount shrinks by (1/2)ⁿ.

Are these 10th grade science worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

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