A Greener Approach for the Measuring of Colligative Properties

Summary

This experiment teaches students the concept of colligative properties using renewable, benign and biodegradable materials. Rather than using conventional solvents with high cryoscopic constants (which are oftentimes aromatics), fatty acids are used explore freezing-point depression. By monitoring the change in freezing points of solutions with varying solute concentrations, students will be able to determine the molecular weight of the unknown solute.

The green aspects of this lab could be further highlighted by a student-generated comparison with a more conventional colligative property experiment.

Supplemental material includes instructor notes, a pre-lab quiz, experimental procedures, calculations sheet and a sample lab report.

Summary prepared January 2009 by Douglas M. Young at the University of Oregon.

Category Descriptors

Chemistry Concepts

• Fatty Acids
• Heating and Cooling Methods (Measurement/Analysis)
• Melting Points and Ranges
• Natural Products
• Phases/Phase Transitions
• Solutions/Solvents

Laboratory Techniques

• Heating and Cooling Methods
• Measuring Mass and Volume

Green Chemistry Principles

• Design for Degradation
• Minimize the Potential for Accidents
• Prevent Waste
• Use Renewable Feedstocks
• Use Safer Solvents/Reaction Conditions

Chemistry Subdiscipline

• Analytical Chemistry
• Interdisciplinary/Multidisciplinary
• Physical Chemistry

Target Audience

• Colleges/Universities
• Secondary Schools

Source

• Journal Articles