A Low-Cost and Simple Demonstration of Freezing Point Depression and Colligative Properties with Common Salts and Ice Cream

Abstract

A laboratory activity was developed to teach freezing point depression and colligative properties to introductory-level chemistry students. The laboratory uses food-grade reagents and is delivered in two units that can be taught in a single 2 hour session or two separate sessions. The total cost of the consumables is 1 USD. In the first part of this two-part activity, students perform measurements on the properties of five salt solutions to better know and understand freezing point depression. In the second part of the activity, students apply their knowledge and understanding of freezing point depression to make ice cream. The ice-cream-making experiment is delivered as a group activity to encourage reflection. Centering this experiment on ice cream allows students to connect properties described in chemistry to everyday life. The solutions used in the experiment are reusable and nonhazardous. The experiment can be implemented in a classroom, in a teaching laboratory, or at home.

A Specifications-Graded, Spice-Themed, General Chemistry Laboratory Course Using an Argument-Driven Inquiry Approach

“…Project #1 focuses on determining an unknown’s identity with freezing and melting points. Many freezing-point depression experiments are known; ,− herein, we use menthol as a solvent and spice compounds as the solute. In the FS session, student teams measure menthol and cinnamic acid melting points using a melting point apparatus.…”