Absolute Dating

Iodine-131 has a half-life of 8 days. After 32 days, how much of your original iodine will be left?

• 50%

• 25%

• 12.5%

• 6.25%

Tags

NGSS.HS-PS1-8

Based on the graph, how much of a substance is left after 2 half-lives?

• 50%

• 25%

• 12.5%

• 6.25%

What is the definition of a half-life?

• The time it takes for a radioactive isotope to decay completely

• Half of the time it takes for a radioactive isotope to decay completely

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

• Half of the life of the Earth

Answer explanation

After one half-life, half of the radioactive material in your sample will have decayed into a daughter isotope.

Tags

NGSS.HS-PS1-8

Based on this graph, about how long is the half-life for Mercury-203?

• 400 days

• 250 days

• 150 days

• 50 days

Answer explanation

A half-life is the amount of time it takes for 50% of the parent isotope to change to the daughter isotope. In other words, when the lines cross, that's one half life.

Tags

NGSS.HS-PS1-8

Over time, what happens to the amount of parent isotope?

• It increases.

• It decreases.

• It stays the same.

• It goes up and down.

Tags

NGSS.HS-PS1-8

Over time, what happens to the amount of daughter isotope?

• It increases.

• It decreases.

• It stays the same.

• It goes up and down.

Carbon-14 is found in once-living organisms and has a half-life of about 5,700 years. Uranium-238 is found in some kinds of rocks and has a half-life of about 4.5 billion years. What would be the best way to find the age of animal bones from a cave?

• Carbon dating

• Uranium dating

• Neither would work

• Both would work

Carbon-14 is found in once-living organisms and has a half-life of about 5,700 years. Uranium-238 is found in some kinds of rocks and has a half-life of about 4.5 billion years. What would be the best way to find the age of a very old rock formation?

• Carbon dating

• Uranium dating

• Neither would work

• Both would work

Tags

NGSS.HS-PS1-8

An archaeologist uses carbon-14 dating to determine the age of wood from a very old shipwreck. She finds that about 50% of the original carbon-14 is left. How old is the ship?

• About 5,700 years

• About 10,000 years

• About 2,350 years

• It's impossible to tell

A radioactive atom breaks down to release energy and particles. What is this process called?

• Fission

• Fusion

• Fracture

• Dating

Tags

NGSS.HS-PS1-8