B EAN 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

C REATE A GRAPH LIKE THIS IN YOUR NOTEBOOK

B EAN D ECAY LAB Q UESTIONS 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?

H OW 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?

S O WHAT IS R ADIOACTIVE ? 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?

T RY T HIS !! 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?