Half-Life Practice

Front

What is half-life?

Back

Half-life is the time required for half of the radioactive atoms in a sample to decay.

Front

If a substance has a half-life of 5 years, how much of a 20 g sample remains after 10 years?

Back

5 g (after 2 half-lives).

Front

What happens to the amount of a radioactive substance after each half-life?

Back

The amount of the substance is reduced by half.

Front

How many half-lives are needed for a substance to decay from 80 g to 10 g?

Back

4 half-lives.

Front

What is the half-life of a substance if 25% remains after 3 half-lives?

Back

The half-life is the time it takes for the substance to reduce to 50%.

Front

If the half-life of a substance is 10 days, how much of a 40 g sample remains after 30 days?

Back

5 g (after 3 half-lives).

Front

What is the formula to calculate remaining mass after n half-lives?

Back

Remaining mass = Initial mass × (1/2)^n.

Front

What is the significance of half-life in radioactive dating?

Back

Half-life helps determine the age of ancient artifacts by measuring the remaining radioactive isotopes.

Front

If the half-life of a substance is 8 days, how much of a 64 g sample remains after 16 days?

Back

16 g (after 2 half-lives).

Front

What is the half-life of iodine-131?

Back

8 days.