Coulomb’s Law is used to explain several properties in the AP Chemistry CED, and we spent our September meeting examining the different situations where Coulomb’s Law is applicable and sharing strategies for helping students craft appropriate responses.
Shifra Yonis kicked off the meeting by discussing how, in Unit #1, Coulomb’s Law is used to explain periodic trends. We reviewed question three from the 2018 free-response exam and some common mistakes that students made when answering the question. Jennifer Cambre shared how Unit #2 requires students to use Coulomb’s Law to describe the interactions of cations and anions in ionic compounds. Question number six from the 2017 free response was reviewed to model commonly seen problems in student responses. Kristen Vanderveen described how Coulomb’s Law can also be used to describe interparticle forces such as ion-dipoles. She presented sample student responses from question one of the recent 2025 free-response exam and several common student errors. Kristen then wrapped up the meeting by presenting a strategy that students can use to write appropriate answers for these types of questions. Students first of all need to be able to correctly identify the particles that are interacting. This avoids the commonly seen mistake of discussing nucleus-electron interactions when answering questions about the interaction between ions and dipoles. Students then need to compare the magnitude of the charges of the particles. If the magnitude of the charges is the same, students should then compare the interparticle distances. After comparing the magnitude of the charges and the interparticle distances, students should use this information and Coulomb’s Law to craft their argument. If there is a higher magnitude of charge, students should be sure to compare the charges and discuss how the higher magnitude of charge leads to greater attractive forces. If the magnitude of the charges is the same, but there is a shorter interparticle distance, students should be sure to discuss the shorter distance between the particles (identifying the particles correctly) and how the shorter interparticle distance will lead to stronger attractive forces. In the breakout rooms, teachers discussed how they differentiate between the application of Coulomb’s Law and any methods they use in their classrooms that are effective in helping their students write better arguments.
What's the attraction with Coulomb's Law?
Video highlights from the September 2025 APTeach Session.
View the PRESENTATION SLIDEDECK and access resource links shared in the full presentation.
Watch the APTeach Session Notes and Updates article for summaries of past meetings and announcements for upcoming presentations.
Each one-hour APTeach Zoom session provides 15-20 minutes of discussion centered around a challenging chemistry topic, followed by breakout rooms that allow small groups of teachers to share their best teaching practices related to that content.
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