Project Title
Potassium-Argon Dating
Author
David Graser, Yavapai College, Prescott, AZ (David_Graser@yc.edu)
Abstract
This contrived project helps students to understand the various methods used to date artifacts and rocks. In this project, each students is given the half-life of Potassium 40 and the amount of Potassium 40 and Argon 40 in a sample (every student gets an amount based on the number of letters in their name). Using this information, they find the age of the sample.
Project Content
Scaffolding Resources
Technology Assignment: Exponential Equations DOC | PDF | VIDEO - This technology helps students to solve an exponential equation using the Method of Intersection in Excel.
Handout DOC | PDF - This document explains how Carbon 14 dating works and can act as a template for the project.
Notes
- I have used this project several times. The toughest part for most students is finding the initial amount. They have a hard time seeing how Potassium 40 gradually changes to Argon 40. The C14 handout was designed to help remedy this problem.
- The concept of finding the constants y0 and k is also tough. Most students can get through finding the constants with a bit of work, but then struggle with using the resulting equation to find the age of the rock sample.
- I require students to solve for the age algebraically, and then to verify the solution graphically. The best students verify that the model equation is correct by checking the the half-life AND verify the age using the Method of Intersection.
- Students will often ask how much they should round the constants. Have them experiment with rounding to different decimal places to see the effect on the age.
