Radioactive Dating
Chapter 11: The History of Life

Scientists use different radioactive isotopes to determine the age of different fossils. You can model radioactive dating if you…

Try This

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1. Place 24 pennies heads-up on a table.
2. Wait 5 seconds, then turn over half of your pennies so that they are tails-up.
3. Repeat Step 2 two more times.
4. Repeat Steps 1 to 3, this time waiting 1 minute before turning over the pennies.
5. Repeat Steps 1 to 3 again, this time waiting 5 minutes before turning over the pennies.

Analyze Your Results

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1. How many pennies remained heads-up after the first half-life?
   How many were tails-up?
   After the second half-life?
   After the third?
2. Which pennies represent atoms of the original samples?
   Which represent the atoms that decayed during each half-life?
3. Which half-life would you choose to date a sample that is approximately 20 seconds old? Which would you choose to date a sample approximately 4 minutes old?

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