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11.4: Lesson 11.3 Nuclear Energy

Difficulty Level: At Grade Created by: CK-12

Key Concept

Nuclear fission is the splitting of the nucleus of an atom into two smaller nuclei. This releases a great deal of energy, which can be used to generate electricity. Nuclear fusion is the fusing of two or more smaller nuclei to form a single, larger nucleus. This releases even more energy than fission, but the energy of fusion has not yet been harnessed for generating electricity. Einstein’s equation, \begin{align*}E = mc^2\end{align*}, explains why a tiny amount of mass changes to such large amounts of energy during nuclear reactions.


  • MCR.6-8.SCI.9.6, 11
  • NSES.5-8.B.3.5; NSES.5-8.F.3.2
  • AAAS.6-8.1.A.3; AAAS.6-8.3.C.1, 3, 5, 7; AAAS.6-8.4.B.9, 12; AAAS.6-8.8.C.2, 4, 10, 11; AAAS.6-8.11.C.3; AAAS.6-8.12.D.6, 11

Lesson Objectives

  • Describe nuclear fission and how it is used for energy.
  • Describe nuclear fusion and challenges to its use for energy.
  • Relate nuclear energy to Einstein’s equation, \begin{align*}E = mc^2\end{align*}.

Lesson Vocabulary

  • nuclear energy: energy released in a nuclear reaction (nuclear fission or nuclear fusion)
  • nuclear fission: splitting of the nucleus of an atom into two smaller nuclei
  • nuclear fusion: fusing of two or more small nuclei to form a single, larger nucleus

Teaching Strategies

Introducing the Lesson

Introduce nuclear reactions with the student-created video at the URL below. It demonstrates a nuclear chain reaction with mousetraps and ping-pong balls and is sure to generate student interest in the topic. Tell students they will learn the science behind the demonstration when they read this lesson.


Discuss the pros and cons of using nuclear energy to produce electricity. Compare it to the use of fossil fuels as well as to alternative energy resources such as solar and wind energy. After the discussion, organize a debate about the use of nuclear energy as an alternative to fossil fuels. Ask a few volunteers to choose sides and then debate the issue in front of the class.


Students can use the excellent simulations at the URL below to explore nuclear fission. In the activity, they can start a nuclear chain reaction and use control rods to limit a nuclear chain reaction in a power plant. Teaching materials are also provided at the Web site.

Building Science Skills

Have students watch and interpret the animated model of nuclear fusion at the following URL. Ask them to identify what the gray and red balls represent in the model (gray balls = neutrons, red balls = protons). Also ask them to identify the reactants and products in the reaction. (The reactants are deuterium and tritium, and the products are helium and a neutron.)

Differentiated Instruction

Partner any English language learners and less proficient readers with other students, and have partners create a Venn diagram comparing and contrasting nuclear fission and nuclear fusion. The area of overlap might include “nuclear reaction” and “releases a lot of energy.” The area limited to fission might include “one large nucleus splits into two smaller nuclei.” The area limited to fusion might include “two small nuclei join into one large nucleus.”


Some students might be interested to learn how nuclear fission was discovered. Have them read and listen to the fascinating first-person account of the story at the URL below. The article is liberally interspersed with recorded statements by some of the main players, including Einstein, Curie, and Meitner. The scientists describe the breakthroughs as they actually happened.

Science Inquiry

Students can explore nuclear reactors by making a model of a nuclear reactor with Activity 2 on page 17 in the following PDF document. In the activity, students use simple materials to make their model and then compare the parts of their model to the parts of a real nuclear reactor (Three Mile Island reactor). They will also research and describe the basic processes that take place in a nuclear reactor.

Real-World Connections

Have students find nuclear power plants in their state or region of the country at the URL below. (They should click on the National Map and then plot all the nuclear power plants.) The map will distinguish operating, proposed, and closed nuclear facilities. Suggest that students do a Web quest to learn more about the nuclear power plant closest to their location.

Reinforce and Review

Lesson Worksheets

Copy and distribute the lesson worksheets in the CK-12 Physical Science for Middle School Workbook. Ask students to complete the worksheets alone or in pairs to reinforce lesson content.

Lesson Review Questions

Have students answer the Review Questions listed at the end of the lesson in the FlexBook® student edition.

Lesson Quiz

Check students’ mastery of the lesson with Lesson 11.3 Quiz in CK-12 Physical Science for Middle School Quizzes and Tests.

Points to Consider

Einstein’s equation is part of a larger theory called the theory of relativity. It is concerned with concepts such as motion and forces as well as mass and energy. Motion and forces are the focus of succeeding chapters.

  • Based on your real-world experiences, how would you define motion?
  • Forces include gravity and friction. How might these forces be related to motion?

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