Pedagogy in Action > Library > ConcepTests > ConcepTest Examples > Conceptest: CFCs and ozone

Conceptest: CFCs and Ozone

David McConnell, Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University

Created with funding from NSF CCLI Award #0087894. Author Profile
This material was originally created for On the Cutting Edge: Professional Development for Geoscience Faculty
and is replicated here as part of the SERC Pedagogic Service.

Question:

Analyze the following student descriptions of the relationship between CFCs and ozone. Which is the best?
a. CFCs are manufactured gases that destroy the ozone layer and produce oxygen.
b. Chlorine forms from the disintegration of manufactured gases. The chlorine reacts with ozone molecules to form two gases that can not block incoming UV radiation.
c. Oxygen molecules are broken down by UV radiation to free oxygen atoms that combine with chlorine monoxide to form new oxygen molecules and free chlorine. Chlorine helps break down CFCs with UV radiation.
d. UV radiation breaks apart complex manufactured chlorofluorocarbons into its constituent atoms, including chlorine. Chlorine destroys ozone molecules as it cycles through a pair of reactions that produce free oxygen molecules.

Student Responses:

Student responses to this question were collected from large (60+ student) introductory Earth Science classes populated by non-majors (mostly freshmen) at an open enrollment Midwestern university. N=163 on first attempt; N=167 after peer instruction)
a. 13% of students chose this answer on their 1st attempt; 0% after peer instruction.
b. 19% of students chose this answer on their 1st attempt; 14% after peer instruction.
c. 26% of students chose this answer on their 1st attempt; 9% after peer instruction.
d. 42% of students chose this answer on their 1st attempt;77% after peer instruction.(correct)

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.