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Conservation of Mass and Energy in Nuclear Reactions

When atoms break apart, energy and matter become interchangeable.

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It All Started with the Nucleus

It All Started with the Nucleus


Credit: Harry Schaefer
Source: http://commons.wikimedia.org/wiki/File:John_Amos_Power_Plant_1973.jpg
License: CC BY-NC 3.0

Giant cooling towers of a nuclear power plant loom over a small house in West Virginia. The power plant generates electricity by splitting apart the nuclei of atoms. Ironically, the scientist who discovered the atomic nucleus thought that harnessing the power of splitting nuclei was nothing but “moonshine.”

The Back Story

  • The atomic nucleus was discovered by the physicist Ernest Rutherford in 1911 in his famous gold-foil experiments. Rutherford also discovered radioactive decay. This is the process in which atomic nuclei break down and give off charged particles and energy.
  • Credit: Wikimedia commons
    Source: http://en.wikipedia.org/wiki/File:Rutherford_gold_foil_experiment_results.svg
    License: CC BY-NC 3.0

    The passing electrons bounced off the nucleus, proving its existence and disproving the plum pudding model (top) [Figure2]

  • In spite of Rutherford’s “moonshine” comment, the world’s first nuclear reactor had been built within 10 years of his discovery of the nucleus. By the 1950s, people were using nuclear fission to generate electricity. Watch this video to see how it’s done: 


Can You Apply It?

Learn more about generating electricity with nuclear fission at the link below. Then answer the questions that follow.

When atoms _____, they break down into atoms of different elements and release energy.

  1. True or false: All atoms eventually decay.
  2. How can fission of an atom of uranium-235 be induced? What happens then?
  3. Why do the products of the nuclear reaction in question 3 all have kinetic energy? How can the amount of that kinetic energy be calculated?
  4. How much more energy is released by the decay of one atom of uranium-235 than is released when a molecule of gasoline (petrol) burns?
  5. Once an atom of uranium-235 decays, why are no more neutrons needed to cause other atoms of uranium-235 to decay?
  6. What is the main difference between nuclear power stations and power stations that burn fossil fuels? How are the two types of power stations the same?
  7. How does the generator work in any power plant?
  8. What is heavy water? How is it used in nuclear reactors?
  9. What are pros and cons of generating electricity with nuclear fission as compared with the burning of fossil fuels?

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Image Attributions

  1. [1]^ Credit: Harry Schaefer; Source: http://commons.wikimedia.org/wiki/File:John_Amos_Power_Plant_1973.jpg; License: CC BY-NC 3.0
  2. [2]^ Credit: Wikimedia commons; Source: http://en.wikipedia.org/wiki/File:Rutherford_gold_foil_experiment_results.svg; License: CC BY-NC 3.0

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