Materials

- 4 bags
- blue beads (U-235)
- green beads (Pb-206)
- red beads (Pb-207)
- yellow beads (U-238)

Procedures

- There are four (4) bags represent four (4) different “fossils”.
- Determine how many half-lives the isotope has gone through and therefore the age of the “fossil”.
- Graph the rate of decay for U-235 and U-238.
- Determine the number of half-lives by locating the % on the graphs.
- U-235 has a half-life of 704 million years
- U-238 has a half-life of 4.5 billion years

(initial # of parent isotopes = # of parent isotopes + # of daughter isotopes)

(# of parent isotopes÷ initial # of parent isotopes × 100 = _____ %)

Data

"Fossil" # # of Parent Isotope # of Daughter Isotope % of Parent Isotope # of Half-Lives Age of "Fossil" 1 ??? ??? ??? ??? ??? 2 ??? ??? ??? ??? ??? 3 ??? ??? ??? ??? ??? 4 ??? ??? ??? ??? ???

Analysis

1. Rank the fossils from oldest to youngest. ???

2. Draw a picture of their relative position in a cross-section layer of soil. ???

3. Why is Uranium used in this case? ???