STEM Chem U1 L6 Isotopes and Radiometric Dating Problem Set

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

• It increases.

• It decreases.

• It stays the same.

• It goes up and down.

Carbon-14 has a half-life of 5730 years.

How long will it take for a sample break down to 1/2 of it's original size?

• 5730 years

• 14 years

• 7 years

• 11,460 years

The unstable Isotope of an element that is considered radioactive.

• parent Isotope

• Half-Life

• daughter Isotope

• Radiometric Dating

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

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.

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

• It increases.

• It decreases.

• It stays the same.

• It goes up and down.

You start with 10 grams of a radioactive material. After 10 days, you test it and find that you have 2.5 grams left. How long is the half-life?

• 10 days.

• 5 days.

• 3.3 days.

• It's impossible to tell.

Answer explanation

After one half-life, 5 grams would be left. After two half-lives, 2.5 grams would be left. Since two half lives have passed in 10 days, the half life is 5 days.

Radiocarbon dating is a type of absolute dating that uses the radioactive isotope __________ to determine how long ago an organism died.

• Carbon-14

• Carbon-12

• Uranium-238

• Carbon dioxide

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

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

• 50%

• 25%

• 12.5%

• 6.25%