BEAN DECAY LAB
1.
How do scientists use radioactive decay or absolute age
to date fossils and artifacts?
2.
How accurate do you think absolute dating
would be? Give me a time frame.

In this lab you are going to start with 100 beans. The
beans represent Uranium atoms. For this lab you will
model how radioactive dating works.
Count your atoms and make sure you have 100
 Place them in the box with all them on the white facing
side.
 Close the lid and shake the box
 Open the box and count the atoms that have the black
side up. After you finish remove them from the box and
graph your results.
 Repeat steps 3 and 4 until you get down to 1 or 0.

Problem:
How many half-lives does it take Uranium to turn
into lead

Hypothesis:
Materials:
Beans, container with lid
CREATE A GRAPH LIKE THIS IN YOUR
NOTEBOOK
BEAN DECAY LAB QUESTIONS
1.
Was your hypothesis correct? Has your definition of “decayed”
changed? If so how?
2.
At the end of each half-life (trial) , approximately what percentage
are the atoms “decaying”?

3. Does the amount of time you shake the box affect the outcome?

4. Do the number of atoms you start with affect the outcome?
Explain. For example if we only used 50 beans, would my data be
different
5. How do you think absolute dating differs from relative dating?


Look at the class master graph…
Why doesn’t everyone have the same results?
 What can this tell us about the accuracy of half
lives?

HOW OLD IS OLD?
Scientists use several strategies to
determine age of rocks and fossils.
1. Relative Age: age of an object compared to
another- “I am older than you”
2. Absolute Age: actual age of an object or
how long ago an event occurred by using
radioactive dating.
3. Radiometric Dating: measures the
absolute age of an object using time or the
rate of decay for a radioactive element
(located in fossils) in a rock

What is radioactivity?
 What does it mean when something is stable or
unstable?
 What are some ways we use radioactive things?


http://www.youtube.com/watch?v=bLszCCLN-uw
SO WHAT IS RADIOACTIVE?


Some atoms are unstable and
breakdown over time in another
form. This process is called
radioactivity
The rate of change or breakdown of
elements is measured in Half-lifes.
Stable = not decayed
 Unstable= decayed


A LOOK AT HALF LIFES
If
Carbon-14 has the half-life
of 5730 years, after 11,400
years approximately how
many half lives would
Carbon of gone through?
TRY THIS!!

If an element was
found with 100 atoms
of Carbon, which has a
half life of 5730 years;
how much will be left
after 3 half lives?