Thursday, February 25th, 2009

Subject: Earth Space Science
Periods: 1, 2, 3, 4/5, 6/7, 10
Length: 50 minutes
State Standard ES. 1.28 Discuss geologic evidence, including fossils and radioactive dating, in relation to Earth’s past.

Lab: Understanding Radiometric Dating

Break the students up into groups of 4. One recorder, one counter, one timer, one motivator.

The students cycle between 5 stations, each with baggies containing two different types of beads that represent parent and daughter isotopes inside of fossils.

Each group of students is to rotate between the each of the 5 stations and complete the following tasks:
1. Count and record the number and color of each of the two types of beads in the bag, without opening the bag.
2. Determine which beads represent the parent atoms and which represent the daughter atoms.
3. Determine the half-life of the parent atom (using the graph provided).
4. Calculate how long ago each fossil formed (by estimating the age from the half-life).
5. Create a time line to determine the order that the fossils formed in.

The formula for determining the percentage of parent isotopes remaining in the fossils is this:
(# parent)/(#parent + #daughter)
... don't forget to covert to a % on the graph and to get the number of half lives!
Use the charts provided by the teacher to know what the time estimates of the half lives for each of the radioactive isotopes are.