The instructor can allot no class time:
Students can benefit from the exhibit through independent study. Students visit the exhibit online and perform exercises assigned by the teacher. For example, one exercise can be chosen from the summary chart and given to the class. Or different exercises can be chosen from the summary chart and assigned by the first letter of the student's last name. Or, as a third alternative, a group of exercises can be offered and each student can choose which avenue to explore.

The instructor can allot one class day:
Students can visit the exhibit as a group during class time. In this case, copies of the text should be available to every student or pair of students. Permission is granted to the instructor to make photocopies of the text for the purpose of providing every student or pair of students with a copy for classroom use. Students may be given one homework assignment prior to seeing the exhibit and one after. The summary chart can help the instructor choose an appropriate task.

The uninterrupted audio track and all the rest of the unit can be purchased at nominal cost on a CD-ROM which can be played in class or made available to individual students who have access to a computer.

MOST TEACHERS WILL PROBABLY FIND THE ABOVE THE BEST WAY TO USE THE EXHIBIT

OR—Teachers may elect to have students view the exhibit independently (see above) and later use class time for discussion and exercises.

The instructor can allot two class days:
DAY 1: Students view the exhibit for half of the class.

The remainder of the class is used for comments on one or more discussion questions, such as those on the accompanying chart.

A homework assignment should be chosen, for example from the summary chart, reflecting teacher or student interest.

DAY 2: Students view the second half of the exhibit.

The beginning of the class may center on reviewing homework or on fresh questions chosen by the instructor. The remainder of the class time may be spent on discussion questions emphasizing the exhibit as a whole.

Homework should be assigned. This might require the reading of an article included in the exhibit or library or Internet research as well as written exercises.

The 5E model of good science instruction recommends that teachers structure the lesson so that it includes the following components: engage, explore, explain, elaborate and evaluate. In using the Discovery of Fission exhibit, teachers can adopt the 5E model in the following manner:

Engage: Students have all heard of nuclear power, nuclear weapons and nuclear medicine and arrive in the classroom with many opinions regarding these technological applications of our nuclear knowledge. Students should be given the opportunity to articulate their prior conceptions. Teachers should be attentive to the students' understanding so that the subsequent instruction can provide a rationale for students to continue their prior beliefs or to replace them based on their study.

Explore: Students can read and listen to the script and begin to explore the events leading to the discovery of nuclear fission. They can continue their exploration by responding to some of the exercises that are designated as "Before visiting the exhibit." These include investigations of the year 1932, the importance of the fission discovery in physics and history, as well as experiments and calculations on the size of the nucleus and decay series. The exploration can continue during the script with a historical perspective on Lise Meitner, science and society discussions on the communications, the media and the nature of discovery in addition to the calculation of energy from fission and the concept of beauty as it relates to physical phenomena.

Explain: Students should study the articles that are included in the exhibit. The original research articles may be a bit difficult in their entirety but should be attempted. Science students get too few opportunities to read any original literature. The other articles and essays were chosen as part of the exhibit because of the different perspectives that they bring to our understanding of the history of nuclear fission.

Elaborate: Students should have the opportunity to apply the knowledge from the script to new situations. Exercises that are denoted "After visiting the exhibit" can be used to focus student attention on the role of chance in history, the excess neutrons required for a chain reaction and Laura Fermi's story of her family's departure from Italy. After their involvement with this exhibit, students can also pursue the larger questions of the societal impact of nuclear technologies including weapons, power and medicine. Much has been written about the decision to drop nuclear bombs on Japan, the arms race and nuclear proliferation. With a foundation in the physics of nuclear reactions, students may wish to pursue a more intensive study of the safety, benefits, dangers and decision making surrounding nuclear power. Some suggestions are included in the Additional Readings and Links.

Evaluate: Many of the exercises can be used as evaluative tools for what students understand and are able to do. The teacher should help students set the criteria for successful achievement. What is the level of expectation in terms of the physics problem solving or the related research items? Evaluations can also include group projects that require students to produce informational pamphlets, to perform or create additional physics simulations, or to compose an essay or play that draws out the human and scientific elements in the history of nuclear fission.

The 4 Question model

The 4 Question model of science instruction requires that students be able to answer the following questions:

• What does it mean?
  
• How do we know?
  
• Why do we believe?
  
• Why should I care?

In using the Discovery of Fission exhibit, teachers can adopt the 4 Question model in the following manner:

What does it mean? Students should be able to explain the physics of nuclear fission including the structure of the atom and nucleus, the nuclear and electrostatic forces and radioactivity. They should also be able to explain the content standards of the National Standards in the domains of inquiry, technology, society and history.

How do we know? We know because we did experiments. How was the scientific information concerning nuclear fission accumulated? What experiments were done? For example, why were Hahn and Strassman uncertain of whether the product was radium and barium? What evidence did Thomson have for the existence of the electron?

Why do we believe? Models for the nucleus and for the fission of the nucleus were proposed. Calculations involving the energy release using E = mc² were shown to be consistent with the experiments. Other, unrelated calculations, involving the electrical potential of the daughter products before fission were also shown to be consistent. The model then makes predictions about stability of nuclei and which nuclei can undergo fission. These predictions are also verified experimentally. We believe because the theories and models make predictions and the predictions are confirmed experimentally.

Why should I care? The nuclear power debate can be more informed if the non-scientific community understands some of the physical principles involved. Questions of safety, radiation damage, and half-lives of waste products must be involved in policy decisions on nuclear power and disposal of nuclear wastes and transportation of nuclear materials. Issues of science policy should include informed debate. Students' lives will be impacted by the costs and availability of adequate power in the future.

A WORD TO THE WISE
Physics teachers may well lack experience in leading discussions. We all know, however, that it is not possible nowadays to think about science without taking account of different viewpoints on social questions. Since the interaction of science and society is often taught only superficially in social studies courses, science teachers need to explore the issues. It is recommended that teachers have a number of discussion questions created or chosen from the chart, so that if one does not develop into a useful class dialogue, a second or third question can be presented.

History teachers frequently lack experience with science demonstrations, problem solving, or explanation of scientific theories. We all know, however, that the citizen can no longer separate understanding of modern history from basic ideas about science itself. Since many students have a very rudimentary science education, a unit in the history of science may be one of their few encounters with scientific reasoning, and it is important to be sure they can follow the logic of the science itself. It is recommended that the instructor test a demonstration before presenting it to the class. Similarly for science problems, a previously worked out solution or explanation will always lead to a better class presentation.

Chart of Exercises
D = Discussion, I = Investigation, R = Research
S = Simple physics problem, C = Complex physics problem