JChemEd Article Describes Density Teaching and Learning Activity

AACT members have access to 50 ACS Publications articles each year. We will be highlighting one article each month that you might consider downloading through this member benefit. This month we are featuring a hands-on student activity from the August 2008 issue of the Journal of Chemical Education titled, The Sweeter Side of Density, by Michael Davis and Charles Henry.

The concept of density is one of the most common topics that all students study in an introductory chemistry class. Unfortunately, they often develop misconceptions during the learning cycle because the examples used in demonstrations and explanations are usually heterogeneous mixtures. This activity is a rare example of using miscible samples to compare density. Students prepare sugar solutions of different concentrations while reviewing the concepts of laboratory techniques and measurements. They then use the solutions to explore the concept of density. You may want to use the Density Animation from the AACT Multimedia Library before completing this activity.

During the first part of this activity, students work in small groups to prepare six sugar solutions of varying concentrations (0% - 50%). This part of the activity can help students practice and improve basic lab techniques, such as measuring mass and volume. Once the solutions are mixed, lab groups exchange samples of their solutions and collect mass and volume data for several samples of each concentration. They then calculate the average density, taking time to discuss errors that might lead to samples of the same concentration having slightly different values for density.

In the second part of this activity, students use food coloring to make each of their solutions a different color. They are then tasked with devising a procedure to layer the different solutions in order of decreasing density. Students are given the time to test their procedures, and present a complete density column to their teacher. This activity also includes extension activities and post-activity questions.

The supporting information for this activity includes a student data sheet, which can be downloaded as a PDF file or Word Document. If you have a favorite ACS Publication article that you use in your classroom, please share it with us at AACTconnect@acs.org.