Exploring the Phases of Carbon Dioxide and the Greenhouse Effect in an Introductory Chemistry Laboratory

Abstract

A safe and inexpensive laboratory for a first-year general chemistry course has been developed which allows students to explore important properties of carbon dioxide, particularly its behavior as a greenhouse gas. Students witness and measure air displacement to compare calculated gas densities and pressures inside a CO2-filled balloon with those of the surrounding air; because the balloon is permeable to CO2, students can determine the average rate of CO2 loss from the balloon. A loosely sealed centrifuge tube containing dry ice allows students to briefly observe liquid CO2 and to map that experience onto the phase diagram of CO2 discussed in lecture. Students simulate the ability of CO2 to act as a greenhouse gas by measuring differences in heat retention in the presence and absence of a CO2-enriched atmosphere within an open beaker containing gravel that serves as a model Earth system. Student reflections indicate substantial gains in a more scientifically rigorous understanding of the role of greenhouse gases in the heating of the atmosphere.