7. Practice: Click Reset. Select the Mystery half-life from the left menu. In this setting, the half-life will be different each time you run the simulation. Run at least three trials. In each trial, measure the half-life using the Half-life probe on the graph. When you have found the half-life, click the camera ( ) icon. Right-click the image, and click Copy. Then paste the image into a blank document, and label each image with the half-life. Print out this document and turn it in with this sheet. 8. Explore: Use the Gizmo to explore whether the number of atoms present affects the half-life that you measure. Describe your findings below:
9. Extend your thinking: The slow decay of radioactive materials can be used to find the age of rocks, fossils, and archaeological artifacts. In a process called radiometric dating, scientists measure the proportions of radioactive atoms and daughter atoms in an object to determine its age. Carbon-14 is a useful isotope because it is found in wood, ash, bone, and any other organic materials. You can use the Half-life Gizmo to model the decay of Carbon-14, which has a half-life of approximately 6,000 years (actual value is 5,730 years). In the Gizmo, select User chooses half-life and Theoretical decay. Set the Half-life to 6 seconds (to represent 6,000 years) and the Number of atoms to 100.
Use the Gizmo to estimate the age of each of the objects below. For these questions, each second in the Gizmo represents 1,000 years.
Description Age (years) Egyptian papyrus with 63% of its original carbon-14 atoms Aboriginal charcoal with 22% of its original carbon-14 atoms. Mayan headdress with 79% of its original carbon-14 atoms Neanderthal skull with 3% of its original carbon-14 atoms