Demonstrations have been used to communicate ideas in chemistry for many years. In introductory classes they are usually presented to illustrate fundamental chemical principles and to promote discussion relating the macroscopic world of chemistry to the molecular and symbolic realms (1). The traditional demonstration/discussion model breaks the monotony of the traditional lecture format and makes the teaching experience more enjoyable. It also fosters the development of a more personal relationship between the instructor and the students and allows students to make a better connection between lecture and laboratory.Recently we described the use of lecture demonstrations to evaluate conceptual understanding and critical thinking skills of K-12 students in physical science (2). In these "demonstration assessments" students view a short demonstration, record their observations, and explain what they observed. Rubrics are applied to score written student responses and promote class discussion. On the basis of this work, one of us (W.C.D.) developed a series of demonstration assessments for freshman chemistry. The study described below was designed to evaluate the effectiveness of the demonstration assessments not only as assessment tools, but also as instruments for developing conceptual understanding and critical thinking.

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Heating the air in a tissue paper balloon using a Merker burner and flying it up and down a guided wire in the classroom.