Laboratory work offers students a practical and tangible experience with chemistry concepts.1 Although safety measures due to COVID-19 have limited or even canceled in-person lab work for many teachers; virtual labs present a reasonable alternative. As described in a previous ChemEd X post, I decided to create virtual laboratory experiments to combine video demonstrations with virtual PhET simulations.
In this activity, students learn about the mole. In section 1, students learn what a mole looks like for different substances. In section 2, students learn how the number of protons and neutrons in the nucleus determines the molar mass of an element by comparing individual isotopes in the PhET simulation, Isotopes and Atomic Mass..
This activity can be completed in one 50 minute class period. The extension “at home” section would require about 30 more minutes.
Section 1 and 2 only require videos and the PhET simulation, "Isotopes and Atomic Mass", Section 3 (at-home investigation) requires a 1-L plastic bottle, 24-inch balloon, vinegar, Alka-seltzer tablets.
Section 1 - What does the Mole Look Like
While students watch a short video, they learn that a mole is a grouping of 6.02 x 1023 things and an immense number. Then, they compare a mole of water molecules to a mole of sugar molecules and notice that the mole of sugar looks larger than the mole of water molecules because sugar molecules are larger than water molecules. Students are introduced to the concept of molar mass by noticing that mass can also describe the amount of each sample. Finally, a procedure to create a mole of CO2 gas from the reaction of vinegar and Alka-seltzer tablets is described and performed. In this demonstration, students notice that volume is more convenient than mass when measuring a mole of gas.
Section 2 - Why Does A Mole Have A Different Mass
In section 2, students start by watching another short video that explains the mass and charge of protons, neutrons, and electrons. They are also introduced to the idea that the mass of isotopes are different because they have different amounts of protons and neutrons.
After watching the video, students explore the PhET simulation, Isotopes and Atomic Mass, to compare the mass and subatomic particles of various isotopes of carbon, nitrogen, and oxygen (image 1).
Image 1: "Isotopes and Atomic Mass" PhET simulation (accessed 10/13/2020).
Section 3 - Try it at Home.
The last, optional section of the lab guide includes a simple lab sheet so that students can carry out the demonstrated experiment on their own.
Most PhET simulations run properly without the need for additional software; however, computers need to be updated regularly to ensure smooth operation. The simulation used in this lab uses Shockwave, a free software plug-in that is preloaded on most devices. PhET also provides a comprensive help center on their website.
Students work through the Virtual Lab: The Mole assignment document (found in the Supporting Information) as described below (image 2). Log into your ChemEd X account for access. The document includes all of the required links to videos and PhET simulations.
Image 2: Example of questions in the student document (available in the Supporting Information)
The student document, including questions, can be found in the Supporting Information below. Log into your ChemEd X account for access.
No teacher preparation is required unless completing the "at home" portion as a demonstration for students.