Many concepts that are important to chemical engineering are introduced and used in thermodynamics courses, but students often solve quantitative problems without having a functional understanding of the concepts involved. Instead, they memorize an algorithm for solving such problems. Qualitative questions that address the important thermodynamic concepts can be used in class, on assignments, and on exams to challenge students with questions that cannot be answered by memorization. These in-class questions are at a level so that only approximately one-third of the students answer correctly initially, even after reading the appropriate sections of the book and discussing the concept in class. Good problems require good wrong answers that show the misconceptions many students have about the material. Examples will be presented to demonstrate the lack of understanding of some of the important concepts in chemical engineering thermodynamics, such as vapor pressure, phase equilibrium, phase changes, reversible and irreversible processes, entropy, fugacity, state functions, chemical equilibrium, ideal gases, energy balances, and cycles.

Many of these conceptual problems use diagrams that represent various behaviors, and many wrong answers are obtained from student answers to conceptual exam questions. These questions are used effectively in class to replace much of the lecture. They are used in combination with student-held remote RF transmitters (clickers) and peer instruction. Students overwhelming like this mode of instruction.