As the teacher looks out at the sea of faces in his or her class, it is hard to tell if the bright eyes reflect any real comprehension. It is easy enough to tell that the guy in the back row reading a newspaper and the girl doodling on her notebook have turned off their minds to chemistry. But what about the ones who seem to be really trying: taking notes, nodding at the right points in the lecture, answering informal questions correctly? They appear to understand, and yet the results of the first examination often prove the contrary--the lights were on but no one was home.

Teaching for understanding, critical thinking, assessment of knowledge rather than facts and procedures learned by rote--all are recurring themes in the articles we publish. Chemistry teachers who read and write for this Journal obviously place a great value on promoting high-order cognitive understanding of the concepts of their subject, but they are also obviously still struggling both to accomplish this goal and to find ways of evaluating how well they have succeeded. A group of articles in this issue reflect various aspects of this struggle and offer a variety of solutions.

While teachers desire their students in the introductory general chemistry course to employ critical thinking, its use is not in much evidence. Kogut (page 218) indicates that the usual structured course does not promote critical thinking and that the teacher must make a conscious effort to redesign the course and to incorporate suitable exercises. He suggests some reasons for student inability to analyze data, recognize assumptions, form hypotheses, and ask probing questions and then explains how he used specific exercises to determine critical thinking levels. While the results were discouraging, he used them to formulate classroom strategies to foster critical thinking that did improve students' abilities.

The introductory course is not the only one that can be redesigned to promote higher-order thinking. Dods (page 225) devised a problem-based approach for the entire biochemistry course, completely reorganizing the curriculum and how it is presented. The course structure emphasizes opportunities for students to engage in dialogues that confirm or disconfirm their understanding of basic concepts. As a result they are observed to have deeper understanding and longer recall of biochemical concepts.

Assessing whether students have actually learned what the teacher thinks he or she has taught is not always easy. Students can mimic verbal explanations and they have such a remarkable capacity for memorizing algorithms that it is often difficult to determine if they understand the concept rather than know a series of superficial manipulations. Smith and Metz (page 233) have confronted this problem in regard to understanding solution chemistry. They found that the traditional mathematically based questions alone could not assess concept knowledge and, therefore, they gave a test using drawings of the microscopic state of particles in solution. When students were asked to draw a microscopic representation to illustrate a reaction in solution, many answers revealed misconceptions regarding acids and bases, acid strength, dissociation, diatomic elements, bonding, and aqueous solutions. Further, when graduate students and faculty were given the same test, it was found that some of these misconceptions persist beyond the undergraduate level.

Given how hard misconceptions are to detect and how long they can persist, it would be useful if teachers could get faster feedback on the success of their teaching strategies. Harwood (page 229) has used a simple tool--the one-minute paper--that does just that. Students were asked at the end of the class to write for a minute on one main point from the lecture and to ask one question they might have. As a result, the teacher gets a sense of how well students understand the topics and can address misconceptions before they become ingrained. And students gain confidence in asking questions and become comfortable with communicating their confusions to the teacher. A different approach to rapid feedback is utilized by Spain (page 222), who has developed computer-interactive homework problem sets for general chemistry. The problems are graded immediately so students can remedy their difficulties and even receive half credit if they subsequently work the problem successfully. The system allows use of different types of questions and includes graphics and animations when applicable.

Feedback about what students know does not have to be immediate to be useful. By evaluating students' strengths and weaknesses at the end of the introductory organic course, Maroto and Camusso (page 231) can apply the results to future planning and design of the course. They prepared a test instrument that allow them to assess the cognitive level of the respondents. They give an example of a question and how it was used to make this assessment, and they discuss how the results will change the course design.