Chapter 6, Lesson 3

Radioactive Dating

Chapter 6, Lesson 3

​Page 234 - 237

What is Radioactive Decay

Radioactive Decay - when elements break down over time and release particles and energy

During radioactive decay, the atoms of one element break down to form atoms of another element

Half-Life

The rate of decay of each radioactive element never changes

Half-Life - the time it takes for half of the radioactive atoms to decay

Multiple Choice

After TWO half-lives, how much of the element remains?

• 50%

• 25%

• 0%

• 75%

Multiple Choice

After THREE half-lives, how much of the element remains?

• 50%

• 25%

• 0%

• 12.5%

Multiple Choice

How many half-lives will it take for the element to be completely gone?

• 1

• 2

• 3

• it will never be completely gone

What is Radioactive Dating?

Radioactive elements are naturally occurring in igneous rocks

Scientists use the rate at which these elements decay to determine the age of the rock

In radioactive dating, scientists first determine the amount of a radioactive element in a rock. Then they compare that amount with the amount of the stable element into which the radioactive element decays.

Potassium-Argon Dating

Scientists date rocks using Potassium-40. This form of potassium decays to argon-40 and has a half-life of 1.3 billion years

Carbon-14 Dating

Carbon-14 is a radioactive form of carbon - all plants and animals contain carbon

When Carbon-14 decays it changes to nitrogen-14

To determine the age of a sample, scientists measure the amount of carbon-14 that is left in the organism's remains

Multiple Choice

Scientists use ___________ to find the absolute age of a rock.

• radioactive dating

• relative dating

Multiple Choice

Most elements do not change.

• true

• false

Multiple Choice

Some elements decay over time.

• true

• false

Multiple Choice

The rate of decay of any radioactive element changes frequently.

• true

• false

Multiple Choice

Radioactive elements occur naturally in sedimentary rocks.

• true

• false

Multiple Choice

Geologists use radioactive dating to determine the absolute age of rocks.

• true

• false

Multiple Choice

All plants and animals contain carbon.

• true

• false

Multiple Choice

An element that has broken down and released particles and energy is said to be _______________.

• sedimentary

• igneous

• radioactive

• a new rock

Multiple Choice

______________ is a method of determining the absolute age of rocks

• relative dating

• rock layering

• radioactive dating

• radioactive decay

Multiple Choice

The time it takes for half of the radioactive atoms in an element to decay is the __________

• absolute age

• half-time

• half-life

• radioactive age

Multiple Choice

During ____________, the atoms of one element break down to form atoms of another element.

• radioactive dating

• rock formation

• radioactive decay

• erosion

Multiple Choice

if there is only 50% of the radioactive element left in a sample, how many half-lives have gone by?

• 1

• 2

• 3

• 4

Multiple Choice

if there is only 25% of the radioactive element left in a sample, how many half-lives have gone by?

• 1

• 2

• 3

• 4

Multiple Choice

Why wouldn't you use Carbon-14 dating to find the age of a piece of igneous rock?

• igneous rock is too young

• igneous rock can't be dated

• igneous rock has no carbon because it wasn't a living thing

• igneous rock doesn't age

Multiple Choice

What is the element that all living things have in common?

• lead

• argon

• carbon

• uranium

Multiple Choice

Looking at this chart, how many years old is the 5.00g sample?

• 2865 years

• 5730 years

• 11460 years

• 17190 years

Multiple Choice

Looking at this graph, can you use carbon-14 to date something that is older than 50,000 years?

• yes because there is more element to decay away

• no because there isn't enough left to decay any more

• it is impossible to tell from this graph

• this isn't a carbon-14 graph

Multiple Choice

What is Cobalt-60's half-life?

• 5.3 years

• 10.6 years

• 0 years

• 15.9 years

Multiple Choice

When there is 12.5% of a Cobalt-60 sample left, how many years old is the sample?

• 5.3 years

• 10.6 years

• 21.2 years

• 15.9 years

Multiple Choice

How much of a sample would be left after 6 half-lives?

• about 10%

• about 12%

• about 3%

• about 1.5%

Multiple Choice

Which is more accurate?

• relative dating

• absolute dating