Visualize!

Let’s face it. There are some pretty abstract concepts covered in chemistry that can be quite difficult for students to visualize. Take for example, the wave-particle duality of light, orbitals, hybridization. When concepts are not naturally “concrete” on their own, it can often help to use pictures or simulations to help students better visualize an abstract concept to which they have never been exposed before.

Today, I would like to focus on the use of PhET simulations to teach about VSEPR theory (with electronic and molecular geometry) and molecular polarity. PhET was founded in 2002 at the University of Colorado Boulder as a way to provide free simulations that allow students and teachers to interact with math and science concepts. These simulations are great to use for the explore phase and can also be used when funding does not cover needed supplies for hands-on experiments in the lab.

In terms of VSEPR theory, PhET provides a simulation called “Molecule Shapes.” This simulation provides 3D molecules (both generic and real) that can be manipulated in 3D to help students visualize electron regions and the changes in geometry that occur due to the presence of lone pairs around the central atom. It allows you to add and remove lone pairs and bonds, check your answers for molecular and electronic geometry, and view bond angles. Since molecular geometry is the actual 3D shape of the molecule, being able to view and rotate these molecules in 3D really

helps students be able to better see the difference between trigonal planar and trigonal pyramidal, bent and linear. When paired with the manipulation of physical model sets, students are left with a much better understanding of geometry.

In relation to molecular polarity, PhET provides a simulation called “Molecule Polarity.” Within this simulation, one can use generic models of molecules to examine how changing the relative electronegativity of certain atoms can affect the dipole moment of the entire molecules. There are features that allow you to show the individual bond dipoles, the overall molecular dipole, and the partial charges on the atoms. Another part of the simulation allows you to examine a variety of real molecules and view the electrostatic potential map and electron distribution map for the molecules. This can be a very effective tool in helping to show students how polar molecules have a distinct positive and negative region due to uneven electron distribution throughout the molecule. This allows students to see how both individual bond polarities and molecular geometry must be taken into account when determining the overall polarity of a molecule.

So, go give PhET a try! Whether you’re teaching on these specific topics or not, check out their many simulations that can help make chemistry concepts less abstract, more accessible, and more engaging for your students!