Fission & Fusion (Edexcel IGCSE Physics)

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  • Name three processes for which nuclear energy is a source.

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  • Name three processes for which nuclear energy is a source.

    Three sources of nuclear energy are:

    • nuclear fusion

    • nuclear fission

    • radioactive decay

  • True or False?

    In both fusion and fission, the mass of the original nuclei is greater than the mass of the products.

    True.

    In both fusion and fission, the mass of the original nuclei is greater than the mass of the products. This missing mass has been converted into energy.

  • True or False?

    Nuclear reactions can be used to generate electricity.

    True.

    Nuclear reactions such as fission and fusion can be used to generate electricity. Fission reactors are already in use in nuclear power plants around the world.

  • Define nuclear fission.

    Nuclear fission is the splitting of a large nucleus into two smaller nuclei.

  • True or false?

    Neutrons and gamma radiation can be released in nuclear fission reactions.

    True.

    Neutrons and gamma radiation can be released in nuclear fission reactions.

  • True or False?

    In a nuclear equation to represent a nuclear fission reaction, a neutron can be represented by straight n presubscript 1 presuperscript 0.

    False.

    In a nuclear equation to represent a nuclear fission reaction, a neutron can be represented by straight n presubscript 0 presuperscript 1.

  • What is a nuclear chain reaction?

    A nuclear chain reaction occurs when

    • 2 or 3 neutrons are emitted from a fission reaction

    • these neutrons cause further fission reactions

    • more neutrons are emitted

    • the rate of fission reactions increases

  • True or False?

    Uranium-235 is an example of a fissile material.

    True.

    Uranium-235 is an example of a fissile material, this means it can undergo fission reactions - its nuclei can be split apart into smaller nuclei.

  • True or False?

    More than one neutron is required to induce fission in a uranium-235 nucleus.

    False.

    Only one neutron is required to induce fission in a uranium-235 nucleus.

  • What happens if the amount of nuclear fuel in a fission reactor is too low?

    If the amount of nuclear fuel in a fission reactor is too low, chain reactions will stop or slow down. This is because neutrons can escape the material without hitting any more nuclei.

  • What happens if the amount of nuclear fuel in a fission reactor is too high?

    If the amount of nuclear fuel in a fission reactor is too high, chain reactions increase rapidly. If uncontrolled, this can lead to a huge release of energy or even a nuclear explosion.

  • What is the purpose of control rods in a nuclear reactor?

    The purpose of control rods is to absorb neutrons.

  • What is the purpose of the moderator in a nuclear reactor?

    The purpose of a moderator is to slow down neutrons.

  • Why must neutrons be slowed down in a nuclear reactor?

    In a nuclear reactor, neutrons must be slowed down so they can react with the uranium fuel efficiently.

    This is because slow neutrons are more likely to be absorbed by a uranium nucleus than fast neutrons.

  • True or False?

    Lowering the control rods in a nuclear reactor increases the rate of fission.

    False.

    Lowering the control rods decreases the rate of fission as more neutrons are absorbed.

  • What is the purpose of shielding in a nuclear reactor?

    The purpose of shielding is to absorb hazardous radiation.

  • What is nuclear fusion?

    Nuclear fusion is the joining of two smaller nuclei to form one larger nucleus, releasing a large amount of energy in the process.

  • True or False?

    The equation below shows a nuclear fission reaction.

    straight H presubscript 1 presuperscript 2 space plus space straight H presubscript 1 presuperscript 1 space rightwards arrow space He presubscript 2 presuperscript 3

    False.

    The equation shows a nuclear fusion reaction

  • True or False?

    In a nuclear fusion reaction, the mass of the fused nucleus is the same as the mass of the two nuclei that fused together.

    False.

    In a nuclear fusion reaction, the mass of the fused nucleus is less than the mass of the two nuclei that fused together. The remaining mass has been converted to energy.

  • True or False?

    The amount of energy released during nuclear fusion is small.

    False

    The amount of energy released during nuclear fusion is huge.

  • What type of reaction is shown in the nuclear equation below, nuclear fission or nuclear fusion?

    straight U presubscript 92 presuperscript 235 space plus space straight n presubscript 0 presuperscript 1 space rightwards arrow space Kr presubscript 36 presuperscript 92 space plus space Ba presubscript 56 presuperscript 141 space plus thin space 3 space straight n presubscript 0 presuperscript 1

    The type of reaction shown in the nuclide equation is nuclear fission.

  • True or False?

    The energy produced during nuclear fusion comes from a very small amount of the particle’s charge being converted into energy.

    False.

    The energy produced during nuclear fusion comes from a very small amount of the particle’s mass being converted into energy.

  • Where do nuclear reactions take place in stars?

    Nuclear reactions take place in the centres (cores) of stars.

  • How is the Sun powered?

    The Sun is powered by the nuclear fusion of hydrogen into helium.

  • True or False?

    Nuclear fusion provides the outward force that prevents stars from collapsing under gravity.

    True.

    The outward force provided by nuclear fusion reactions prevents stars from collapsing under gravity.

  • True or False?

    Nuclear fusion requires extremely high temperatures to maintain.

    True.

    Nuclear fusion requires extremely high temperatures to maintain.

  • What two conditions are required for nuclear fusion to occur?

    The two conditions required for nuclear fusion to occur are:

    1. High temperature

    2. High pressure or density