Free Printable Half-Lives

1.

Geologist use the time it takes for a radioactive isotope to decay to half its original mass called a___________.

a)

radioactive decay

b)

isotope

c)

half-life

d)

carbon dating

2.

The half life of a sample is 5 days. How many half lives have passed in a period of 15 days?

a)

1

b)

2

c)

3

d)

4

3.

What is the half life of this sample?

a)

2 mins

b)

3 mins

c)

4 mins

d)

4 hours

4.

How old is this fossil after undergoing 4 half-lives?

(a)

5.

The amount of time it takes for half of the particles of an element to decay is called:

a)

Absolute Age

b)

Half-Life

c)

Radioactivity

6.

The half - life of radon - 222 is 3.8 days. How much of a 100 g sample is left after 15.2 days.

a)

50.0 g

b)

25.0 g

c)

12.5 g

d)

6.25 g

7.

The time required for half of the parent isotope to decay into daughter isotopes.

a)

Absolute Age

b)

Relative Age

c)

Fossil

d)

Half-life

8.

What is the half-life of a radioactive element?

a)

How old it is when it is middle aged

b)

The time it takes for half of the atoms to decay

c)

The time it takes for half of the atom to form

d)

How old it is when the Earth is middle aged

9.

The half - life of K - 42 is 12.4 hrs. How much of a 750 g sample is left after 62.0 hrs?

a)

187.5 g

b)

93.8 g

c)

46.9 g

d)

23.4 g

10.

A 50.0 g sample of N - 16 decays to 12.5 g in 14.4 seconds. What is it's half - life?

a)

14.4 sec

b)

7.2 sec

c)

3.6 sec

d)

1.8 sec

11.

Suppose you extract one gram of carbon from an ancient wooden hammer handle. You find that your ancient gram of carbon is half as radioactive as a gram of carbon extracted from a tree branch that was cut today. The half-life of C-14 is 5,730 years. Assuming that today’s ratio of C-14 to C-12 is the same as when the hammer was made, how old would you estimate is the hammer?

a)

1,432.5 years old

b)

2,865 years old

c)

5,730 years old

d)

11,460 years old

12.

Suppose you extract one gram of carbon from an ancient wooden hammer handle. You find that your ancient gram of carbon is half as radioactive as a gram of carbon extracted from a tree branch that was cut today. The half-life of C-14 is 5,730 years. Assuming that today’s ratio of C-14 to C-12 is the same as when the hammer was made, how old would you estimate is the hammer?

a)

1,432.5 years old

b)

2,865 years old

c)

5,730 years old

d)

11,460 years old

13.

Based on the graph, what is the approximate number of radioactive atoms of Isotope X that are present when 4 hours of decay has occurred?

a)

1000

b)

500

c)

400

d)

50

14.

What percentage of Rubidium-87 will be remaining after 4 half lives?

a)

50%

b)

25%

c)

12.5%

d)

6.25%

15.

Why is Carbon-14 NOT useful in dating rocks?

a)

It is does not have predictable decay rates

b)

Its half life is too short so there is not measurable organic material remaining

c)

It has a long half life

16.

After the third half-life, how much of the sample is left?

a)

1/2

b)

1/3

c)

1/16

d)

1/8

17.

For which of the following problems would a scientist most likely use carbon-14?

a)

to calculate the age of the Earth's oldest rocks

b)

to calculate the age of a piece of bone

c)

to identify the elements that make up a rock

d)

to identify the elements that make up a bone

18.

Which radioactive isotope takes the greatest amount of time to disintegrate? (Use p 1 of ESRT)

a)

potassium-40

b)

uranium-235

c)

uranium-238

d)

rubidium-87

19.

Why is Carbon -14 useful in dating ages of fossils?

a)

It has a predictable, regular decay rate

b)

Its halflife is 20 years

c)

It disintegrates fossils

d)

It is not radioactive

20.

Identify the element formed when Carbon-14 undergoes radioactive decay.

a)

U-238

b)

N-14

c)

Ru-87

d)

C-14

21.

What does the term "half-life" mean in radioactive dating?

a)

The time it takes for half of the parent isotope to decay into daughter isotopes

b)

The time it takes for all isotopes in a sample to decay

c)

The average age of a fossil sample

d)

The amount of time a radioactive element stays stable

22.

Which of the following best describes the concept of half-life in radioactive decay?

a)

The time it takes for half of the radioactive atoms in a sample to decay

b)

The time it takes for all radioactive atoms in a sample to decay

c)

The time it takes for a radioactive sample to become completely stable

d)

The time it takes for a radioactive sample to lose all its mass

23.

A scientist measures a radioactive sample and finds that only 25% of the original radioactive atoms remain. How many half-lives have passed?

a)

1

b)

2

c)

3

d)

4

24.

If a radioactive isotope has a half-life of 10 years, how much of a 100g sample will remain after 30 years?

a)

50g

b)

25g

c)

12.5g

d)

6.25g

25.

Which real-world application relies on the concept of half-life to determine the age of ancient artifacts?

a)

Carbon dating

b)

Thermal imaging

c)

Magnetic resonance imaging

d)

X-ray crystallography

Half-Lives

Total questions: 25

Worksheet time: 25mins

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