Mass, Energy and the Unified Atomic Mass Unit · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Mass is frozen energy

Science · Matter & Materials · ages 17-18
Name ______________________   Date ____________

  1. One nuclear reaction releases millions of times more energy per particle than one chemical reaction. True or false?

    Circle one:   True   False

  2. What does E equals m c squared tell you about mass and energy?

    • Mass times c squared equals the matching energy
    • Mass plus c equals the matching energy
    • Mass divided by c squared equals the matching energy

  3. Boiling a kettle adds energy, yet its mass seems unchanged. Why?

    • Heating uses no real energy
    • Mass disappears whenever water boils
    • c squared is enormous, so the gain is unweighable

  4. One nuclear reaction releases millions of times more energy per particle than one chemical reaction.

    Circle one:   True   False

  5. One atomic mass unit of matter is fully converted to energy. Roughly how much energy is that?

    • About 930 MeV
    • About 1 MeV
    • About 13.6 eV
    • About 3.2 MeV

  6. A reaction loses 0.002 kg of mass. Use c = 3.0e8 m/s with E = m c squared. How much energy is released in joules?

    Answer: ______________

  7. A particle of mass 3.0e-28 kg is created from energy. Use c = 3.0e8 m/s. How much energy did it take in joules?

    Answer: ______________

  8. A reaction loses 0.002 kg of mass. Use c = 3.0e8 m/s with E = m c squared. How much energy is released in joules?

    Answer: ______________

  9. A particle of mass 3.0e-28 kg is created from energy. Use c = 3.0e8 m/s. How much energy did it take in joules?

    Answer: ______________

  10. Reaction A loses twice as much mass as reaction B. How do their released energies compare?

    • A releases twice as much
    • Both release the same
    • A releases half as much
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Mass is frozen energy W1-mt_GTfhALD90X-s1

  1. True · Nuclear rearrangements tap the nucleus, worth millions of times more per particle than electron shuffles.
  2. Mass times c squared equals the matching energy · c squared is the exchange rate between the mass unit and the energy unit.
  3. c squared is enormous, so the gain is unweighable · The added mass is E over c squared, a speck no balance can detect.
  4. True · Nuclear rebuilds pay millions of eV each, while electron shuffles pay a few eV.
  5. About 930 MeV · One atomic mass unit converts to about 931 MeV, millions of times a chemical share.
  6. 180000000000000 · E = m c squared = 0.002 x 9.0e16 = 1.8e14 J.
  7. 2.7e-11 · Multiply 3.0e-28 by 9.0e16: fronts give 27 and powers give e-12, so 2.7e-11 J.
  8. 180000000000000 · Square c to get 9.0e16, then multiply by 0.002 to get 1.8e14 J.
  9. 2.7e-11 · E = 3.0e-28 x 9.0e16 = 27e-12 = 2.7e-11 J.
  10. A releases twice as much · Energy follows mass directly through c squared, so double mass means double energy.
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