AACT Resources to Teach Intermolecular Forces and Periodic Trends in AP Chemistry

By Kim Duncan on April 17, 2017

The concepts of intermolecular forces (IMFs) and periodic trends are both quite difficult for students to understand and explain. It seems even more challenging for them to answer higher level questions related to ionization energy and atomic or ionic radius, especially when the questions require students to make comparisons between two substances with reference to these specific properties. There are several learning objectives in the AP Chemistry Curriculum Framework that are found in Big Ideas 1, 2, and 5 related to these topics. The AACT high school resource library has several classroom activities that will help your students learn and apply these two concepts.

After introducing the concept of IMFs, (London dispersion forces, dipole-dipole forces and hydrogen bonding) use the Intermolecular Forces Simulation to allow your students to compare the strength of each force. This activity, allows students use the Comparing Attractive Forces simulation was created by the Concord Consortium for AACT using Next-Generation Molecular Workbench software, to investigate different types of IMFs. The analysis questions available in the accompanying lesson plan lead the students to make connections between IMFs and physical properties, such as boiling point and solubility. By the end of the lesson, students will better understand the relative strengths of IMFs and their effect on physical properties. This simulation and accompanying lesson were published in the November 2014 issue of Chemistry Solutions.

Follow up the simulation activity with the Physical Properties lab, which allows students to investigate how IMFs affect the melting point and solubility of common materials. The data collected during the lab will help students recognize that physical properties are related to IMFs. It will also improve their understanding of what happens during freezing and melting phase changes, as well as how IMFs are related to dissolving and solubility.

Finally, use the Intermolecular Forces Review lesson plan to lead your students through a review of the concept of IMFs using a PowerPoint presentation and student worksheet. The presentation will help your students better explain and distinguish between London dispersion forces, dipole-induced dipoles, dipole forces, hydrogen bonding, and ionic bonding.

Introduce the concept of atomic radius with the Atomic & Ionic Radii animation to give your students the opportunity to visualize and differentiate between atomic and ionic radii. They will observe different sizes of atoms in the third period and the atoms in the sixth group. They will also look at an atom and compare it to its cation, as well as compare an atom with its anion.

The Periodic Trends II: Electron Affinity, Atomic Radius & Ionic Radius lesson plan and accompanying simulation focuses on the electron affinity of an atom. Through the use of this simulation students will have the opportunity to examine the formation of an anion as well as compare the atomic radius of a neutral atom to the ionic radius of its anion. This lesson and simulation were published with the May 2016 issue of Chemistry Solutions.

Finally, use Mendeleev's Periodic Table activity to allow your students to use their knowledge of Periodic Trends to analyze and identify unknown elements and organize them correctly in the Periodic Table. Two sets of “Mendeleev Cards” are included with this activity. One set includes ten unknown elements. The other includes the names and property information of all of the elements and can be used as a template to customize this activity to fit the needs of your students. Additionally, this activity can be used as a summative assessment. You can find links to other AACT resources to teach periodic trends in a news post from March 2016.

We are working hard to expand our library of classroom resources for AP Chemistry teachers. Do you have a great AP demonstration, activity, or lesson about IMFs or periodic trends that you would like to share with the community? We are proud to feature teacher-submitted activities in our classroom resource collection. If you want to share something you use in your classroom with the community, please send it along for consideration.