ConcepTest: What percentage of parent isotopes remain?

ConcepTest questions by David McConnell , David Steer , Walter Borowski, Jeffrey Dick, Annabelle Foos, Jeffrey Knott, Alvin Konigsberg, Michelle Malone, Heidi McGrew, Kathie Owens, and Stephen Van Horn

Created with funding from NSF CCLI Award #0087894.
This material was originally created for Starting Point:Introductory Geology
and is replicated here as part of the SERC Pedagogic Service.

Initial Publication Date: May 8, 2006

Related Links

Question:

The half-life of a radioactive isotope is 1,000 million years. Scientists testing a rock sample discover that the ratio of parent and daughter isotopes indicates that the rock is 3,000 million years old. What percentage of parent isotopes remain in the sample?

a. 40
b. 25
c. 12.5
d. 5

Student Responses:

No data yet. The correct response is c.

If you would like to help acquire more Before and After statistics for this example, please contact the authors (see link at top of page).

References and Notes:

The use of ConcepTests and Peer Instruction is discussed in detail on the ConcepTest page.

McConnell, D.A., Steer, D.N. and Owens, K.A., 2003, Assessment and Active Learning Strategies for Introductory Geology Courses, Journal of Geoscience Education, 51(2), 205-216.

McConnell, D.A., Steer et al., 2006, Using Conceptests to Assess and Improve Student Conceptual Understanding in Introductory Courses, Journal of Geoscience Education, (54(1), 61-68.