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Content Benchmark P.12.C.3
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Students know nuclear reactions convert a relatively small amount of material into a large amount of energy. I/S

The nucleus of an atom contains two primary particles, the neutron and the proton. When protons and neutrons form a nucleus, the process involves the conversion of some of the mass of these particles into energy. This is given by Einstein’s famous equation: E=mc2. The actual mass of the nucleus is slightly less than when you add the mass of the protons added to the mass of the neutrons. This loss represents mass that has been converted to energy.

For more information refer to

In Einstein’s equation, the amount of mass is multiplied by the speed of light squared
(c2 ~ 9 × 1016 m2/s2), which is a tremendous quantity. Therefore, a small amount of mass results can be converted to a substantial amount of energy.

When electrons move from one quantum orbital to another, they emit or absorb visible light energy. Conversely, in the nucleus of an atom as the protons and neutrons come together, they emit gamma ray photons, which are much more energetic than visual light photons. For more information about this process refer to

In processes that involve nuclear changes that is, nuclear fission or nuclear fusion, massive amounts of energy are released through the conversion of mass into energy. The table below compares the energy released in combustion (chemical) to that released in the fission and fusion nuclear reactions.

  Chemical Fission Fusion
Sample Reaction C + O2 → CO2 n + U-235 → Ba-143 + Kr-91 + 2 n H-2 + H-3 → He-4 + n
Typical Inputs (to Power Plant) Bituminous Coal UO2 (3% U-235 + 97% U-238) Deuterium & Lithium
Typical Reaction Temperature (K) 700 1000 108
Energy Released per kg of Fuel (J/kg) 3.3 x 107 2.1 x 1012 3.4 x 1014

Scientists have long known that nuclear fusion occurs in the sun and in distant stars. Stars are the building machines of the known elements. Atoms of hydrogen combine to form helium atoms which combine to form larger elements. Upon violent explosions of massive stars, called supernovae, elemental material is spewed throughout the universe.

For further information about supernovae, go to

Practical applications of nuclear fusion and fission occur on Earth only in human-made laboratories. Radioactive decay (fission processes) does occur in the Earth’s mantle, driving convective processes. However, on the surface, fission is a human-made activity.

Nuclear Fission

When nuclear fission occurs, an atom is split into one or more progeny products. In this reaction, some of the nuclear mass is converted to energy. With the large amounts of nuclei involved, a tremendous amount of energy is released. The first nuclear fission reactions were researched and developed for military uses during World War II.

Figure 1. A schematic of fission of U-234

To learn more about fission reactions in nuclear bombs, go to

Since World War II no nuclear bombs have been detonated on a population. Many devices have been tested throughout the years and in Nevada, the Nevada Test Site has been used for atomic testing.

To learn more about the Nevada Test Site, go to

Nuclear power plants sought to use the fission reaction to generate the heat needed to drive turbines in a process to generate electricity. This process offered an alternative to coal-fired power plants of the 1950’s. Dirty air, acidic rain, and health hazards due to smog fueled interest in the building and design of nuclear power plants. Nuclear energy is one solution to a dependence on fossil fuels.

To learn more about nuclear power plants, go to

For a discussion on the economics of nuclear power plants, go to

Nuclear Fusion

When nuclear fusion occurs, two or more lighter elements combine to form a heavier atom. As with nuclear fission, some of the nuclear mass is converted to energy during the reaction.

Electrical power generation using nuclear fusion is currently being researched as an alternative to nuclear fission. Nuclear fusion is also used for military purposes in the development of the nuclear fusion bombs which are also known as thermonuclear devices. They are more efficient than nuclear fission bombs. Teller-Ulam designed a bomb that incorporated a fusion reaction which was detonated by a fission reaction - a bomb within a bomb.

For further information about thermonuclear weapon, please see

Fusion reactors have not been practical in the laboratory given that the temperatures required to fuse two hydrogen atoms is millions of degrees Celsius. However, it has been estimated that a gallon of water could contain the energy potential of 300 gallons of gasoline. Research is being done to develop fusion reactors that are practical and safe.

For more information on nuclear fusion go to: and

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Content Benchmark P.12.C.3

Students know nuclear reactions convert a relatively small amount of material into a large amount of energy. I/S

Common misconceptions associated with this benchmark:

1. Students confuse the terms nuclear fission and nuclear fusion or that fission is more powerful than fusion.

This misconception probably stems from the words being similar. Also, because nuclear fusion and fission are often discussed in specific unit, this confusion is understandable. Also, with fission being associated with the World War II atomic bombs, students may think that these reactions are more energetic than fusion, on a mass per mass basis.
More about fission and fusion confusion can be found at

2. Students incorrectly believe that nuclear power plants explode like nuclear bombs.

The reactor accident at Chernobyl caused this belief. While a large explosion and fire occurred during the Chernobyl accident, the facility was an old graphite reactor design that is inherently unsafe. Modern nuclear reactors are designed to generate heat to boil water which turns a turbine generating electricity and the core is confined and has many safety features to safeguard the plant. In other words, current reactor designs would make a Chernobyl-type disaster nearly impossible.

To learn more about modern reactor designs and misconceptions associated with nuclear power, go to

3. Students incorrectly believe that radioactivity first appeared during World War II

Radioactivity is a natural process and current scientific models support that radioactivity has been around since the universe’s origin. Humans have known about radioactivity and used it since the 19th century.

More about this misconception and others associated with nuclear reactions can be found at

4. Students incorrectly think that atoms cannot be changed from one element to another.

Atoms can be changed to new elements with the addition or subtraction of protons. We see atoms change in alpha decay, fission and fusion reactions. Students can confuse changing of an element by addition or subtraction with a proton with isotopes. Isotopes are in fact the same element where the number of neutrons differs.
To learn more about isotopes, go to

5. Students incorrectly believe that nuclear power plants are the only type of electrical generation that produces radioactive waste.

Combustion of coal is the most common way to generate electricity in the United States, as well as other major industrial countries (e.g., China). In the mining of coal, trace amounts of naturally occurring radioactive material (uranium and thorium) are brought to the surface. Some of this uranium and thorium is distributed to the environment through the plant’s stack. While much of the radioactive material is captured in the plant’s air pollution control equipment, some quantity is released into the atmosphere and does present a risk to those living near the coal plant. The U.S. EPA monitors releases of radioactive materials from coal stacks to ensure that releases are under those prescribed to protect public health and safety. Radioactive wastes are also created from drilling of oil and natural gas.

To learn more about generation of radioactive waste, go to
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Content Benchmark P.12.C.3

Students know nuclear reactions convert a relatively small amount of material into a large amount of energy.

Sample Test Questions

1st Item Specification: Distinguish between fission and fusion, and provide examples of each.

Depth of Knowledge Level 1

  1. Nuclear fusion reactions
    1. involve an atoms’ electrons reacting, transforming large amounts of energy.
    2. occur commonly on Earth using large amounts of energy to warm the Earth’s core.
    3. cause large atoms to divide into smaller atoms releasing large amounts of energy.
    4. cause smaller atoms to combine into larger atoms releasing large amounts of energy.
  1. Nuclear fusion reactions
    1. are responsible for the formation of most elements.
    2. are commonly used in nuclear power plants.
    3. are used in Russian-style nuclear reactors.
    4. occur when electrons combine with neutrons.
  1. Nuclear fission reactions
    1. are responsible for the formation of most elements.
    2. are commonly used in nuclear power plants.
    3. are the reactions that power the stars.
    4. occur when neutrons decay into electrons and protons.
  1. Nuclear fission was first developed for
    1. medicinal purposes.
    2. to replace fossil fuels.
    3. military purposes.
    4. as a replacement for steam engines.
  1. When the uranium nucleus splits into smaller nuclei, what type of reaction occurs?
    1. Fission
    2. Fragmentation
    3. Fusion
    4. Fermentation
  1. In the Sun, nuclear fusion causes hydrogen nuclei to fuse and form
    1. iron.
    2. potassium.
    3. uranium.
    4. helium.

Depth of Knowledge Level 2

  1. The following diagram shows uranium-235 reacting forming barium, krypton, more neutrons, and also releasing energy. Use the diagram to answer the following question.

(Click Image to Enlarge)

This reaction represents nuclear

  1. fission.
  2. fusion.
  3. transmutation.
  4. decay.
  1. Use the diagram below to answer the following question

(From ttp://

Which of the following best describes the reaction?

  1. Nuclear decay
  2. Nuclear fusion
  3. Nuclear fission
  4. Translocation
  1. Nuclear fusion differs from nuclear fission because during nuclear fusion
    1. energy does not change during fusion reactions.
    2. smaller nuclei are combined into a larger nucleus.
    3. larger nuclei are combined into one nucleus.
    4. large nuclei are split into smaller nuclei.

2nd Item Specification: Know that a large amount of energy is produced from a relatively small amount of material in a nuclear reaction.

Depth of Knowledge Level 1

  1. Nuclear fission and nuclear fusion reactions cause
    1. atomic nuclei to change.
    2. electrons to release large amounts of energy.
    3. protons and electrons to fuse.
    4. neutrons and electrons to fuse.
  1. In nuclear reactions, some mass is converted into
    1. protons.
    2. electrons.
    3. matter.
    4. energy.
  1. When nuclear reactions are compared with ordinary chemical reactions, one MAJOR difference is
    1. he amount of energy released in nuclear reactions.
    2. the amount of matter absorbed in nuclear reactions.
    3. the loss of energy in chemical reactions.
    4. the gain of energy in chemical reactions.

Depth of Knowledge Level 2

  1. Currently, commercial nuclear power plants in the United States require a radioactive isotope that can
    1. fission and convert energy to matter.
    2. fission and release a large amount of energy.
    3. fuse and release a large amount of energy.
    4. fuse and convert energy to matter.
  1. Which of the following types of reactions will release the MOST energy per kilogram of reactant?
    1. Synthesis reactions
    2. Combustion processions
    3. Nuclear fusion
    4. Dynamite reactions
  1. In terms of mass–energy conversion, which of the following releases the greatest amount of energy per kilogram of reactant?
    1. Fusion
    2. Fission
    3. Combustion
    4. Nitrogylcerine
  1. One of the major drawbacks to harnessing nuclear fusion for practical purposes is the
    1. amount of isotope needed to start the reaction.
    2. release of neutrons to the environment.
    3. high temperatures needed to start the reaction.
    4. low pressure needed to contain the reaction.
  1. Which of the following releases the most energy per kilogram of reactant?
    1. Bituminous coal
    2. Uranium-235
    3. Natural gas
    4. Petroleum
  1. Nuclear fusion is difficult to harness because
    1. hydrogen is very expensive to obtain in pure form.
    2. low starting temperatures and large containment facilities.
    3. high starting temperatures and containment problems.
    4. heavy nuclei are needed at low temperatures.

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Content Benchmark P.12.C.3

Students know nuclear reactions convert a relatively small amount of material into a large amount of energy.

Answers to Sample Test Questions

  1. D, DOK Level 1
  2. A, DOK Level 1
  3. B, DOK Level 1
  4. C, DOK Level 1
  5. A, DOK Level 1
  6. D, DOK Level 1
  7. A, DOK Level 2
  8. C, DOK Level 2
  9. B, DOK Level 2
  10. A, DOK Level 1
  11. D, DOK Level 1
  12. A, DOK Level 1
  13. B, DOK Level 2
  14. C, DOK Level 1
  15. A, DOK Level 1
  16. C, DOK Level 2
  17. B, DOK Level 1
  18. C, DOK Level 2

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Content Benchmark P.12.C.3

Students know nuclear reactions convert a relatively small amount of material into a large amount of energy. I/S

Intervention Strategies and Resources

The following is a list of intervention strategies and resources that will facilitate student understanding of this benchmark.

1. The Savage Sun
The Discovery Channel’s “Savage Sun” video focuses on recent understanding of the Sun through space-based solar missions. The basic description can be found at

An associated lesson plan can be found at

2. Modeling Nuclear Fusion in the Sun
The National Solar Observatory (NSO) invites selected teachers to participate in summer research experiences.

From one former participant, Joey Rogers, comes this activity to model nuclear fusion in the Sun:

3. Contemporary Physics Education Project (CPEP)
This website contains several pages of explanation, diagrams, and activities relating to fusion. The project was sponsored by the US Department of Energy and the University of California Lawrence Livermore National Laboratory.

To access the CPEP site, go to

4. Modeling Layers in a Massive Star
NASA’s Imagine the Universe site contains many lessons and activities that concern astronomical processes, such as nuclear fusion. One of the activities allows students to model the layers of a massive star that result from a series of nuclear fusion reactions.

To see this lesson, go to

5. ABC’s of Nuclear Science
The Lawrence Berkeley Lab has created a comprehensive Web site discussing the fundamental of nuclear science. This site gives excellent background in the chemistry and physics of nuclear science including teacher materials and experiments, as well as posters and other teacher’s guides.
To learn more, go to

6. Radioactivity Background Information
This site provides the student and the teacher with solid background information on radioactivity and can be found at

7. Nuclear Medicine Information Sheet
Radioactivity, Isotopes and Radioisotopes from Nature, Nuclear Reactors and Cyclotrons for use in Nuclear Medicine

8. Fission Simulations
The University of Colorado’s PhET site contains many physics simulations that can be used to by students to understand mechanical, electrical, and nuclear processes. This site provides good simulations for nuclear fission processes that can be accessed in the “Quantum Phenomenon.”

To access the site home page, go to and then click on “Quantum Phenomenon” in the left hand tool bar.

9. The History of Nuclear Energy
The University of Missouri at Rolla has created extensive background information on nuclear energy. This site can be used by students for research and is found at

10. Nuclear Weapons-Basics
The Nuclear Age Peace Foundation has created an interesting compilation of information regarding development of nuclear weapons and their use. This site can be used by students for research and is found at key-issues/nuclear

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