Half-Life

Open Ended

How do you think the concept of half-life can be applied to real-world problems or discoveries?

Multiple Choice

Which of the following best describes why radioactive decay is considered both random and predictable?

• Each atom decays at a fixed time.

• All atoms decay simultaneously.

• Individual atoms decay randomly, but large groups decay predictably.

• Decay only happens in certain elements.

Multiple Choice

Which of the following isotopes has the shortest half-life?

• Uranium-238

• Carbon-14

• Polonium-214

• Nitrogen-14

Multiple Choice

Which of the following statements about half-life is correct?

• Half-life is the time it takes for all of a sample to decay.

• Half-life is the time it takes for half of a sample to decay.

• Half-life is the time it takes for a sample to double in size.

• Half-life is unrelated to radioactive decay.

Fill in the Blanks

The formula to calculate the percent remaining after a certain number of half-lives is starting amount divided by

to the power of the number of half-lives.

Open Ended

Explain how the concept of half-life helps scientists estimate the age of ancient objects.

Multiple Choice

After 24 years, 8g of an original 128g sample remains. What is the half-life of the sample?

• 3 years

• 6 years

• 8 years

• 12 years

Multiple Choice

Which of the following is a real-world application of carbon-14 dating?

• Dating ancient rocks

• Dating once-living things up to about 50,000 years old

• Measuring radiation at nuclear sites

• Determining the age of the universe

Multiple Choice

Why is understanding radioactive decay important for scientists studying the past?

• It helps scientists predict the weather

• It allows scientists to date ancient artifacts and fossils

• It is used to create new elements

• It helps scientists grow plants faster

Multiple Select

Which statements about half-life and radioactive decay are correct? Select all that apply.

• After 2 half-lives, 50% of the original sample remains.

• Carbon-14 dating is effective for biological samples up to about 50,000 years old.

• If uranium-238 has a half-life of 4.5 billion years, then after 9 billion years, about 25% of the original sample would remain.

• A fossil with 12.5% of its original carbon-14 has undergone three half-lives and is approximately 17,190 years old.

Multiple Choice

Which of the following is NOT a misconception about half-life or radioactivity?

• All isotopes decay at the same rate

• Radioactivity means instant danger

• Half-life means half the time to disappear

• Longer half-life means slower decay and lower radioactivity

Open Ended

Explain why radioactivity does not always mean instant danger, using the concept of half-life.

Fill in the Blanks

Fill in the blank: The half-life is the time for

of a sample to decay.

Fill in the Blanks

The half-life of a radioactive isotope is the time it takes for half of the original amount to

.

Open Ended

What is one real-world application of the concept of half-life that you found most interesting, and why?

Multiple Choice

How many half-lives have passed if 12.5% ¹⁴C remains?

• 1 Half-life

• 2 Half-lives

• 3 Half-lives

• 4 Half-lives

Multiple Choice

What percent of carbon-14 would be left after 11,460 years?

• 100%
• 75%
• 50%
• 25%