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Year 11
AQA
Foundation

Nuclear fission and fusion

I can explain how energy can be transferred from the nuclei of atoms to cause heating.

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New
New
Year 11
AQA
Foundation

Nuclear fission and fusion

I can explain how energy can be transferred from the nuclei of atoms to cause heating.

Download all resources
Share activities with pupils

Lesson details

Key learning points

  1. Nuclear fission is the splitting of a large and unstable nucleus such as uranium or plutonium.
  2. A neutron fired at a uranium nucleus can cause nuclear fission that splits the nucleus and emits 2 or 3 more neutrons.
  3. The motion of all the particles shot out from a nuclear fission can cause heating by making other particles move faster.
  4. Neutrons shot out from a nuclear fission can split more uranium nuclei in a chain reaction.
  5. Nuclear fusion is the joining of two light nuclei to form a heavier nucleus with the creation of gamma radiation.

Common misconception

Radioactive isotopes disappear when they decay, so that in one half-life half the mass is lost.

Emphasise that the mass of the nuclei at the end of a nuclear fission or fusion are almost identical to the masses of those at the start. There is a very small difference, with mass being converted to energy according to E = mc².

Keywords

  • Nuclear fission - the splitting of large nuclei to form pairs of smaller nuclei and some free neutrons, with the release of energy

  • Daughter nuclei - the smaller nuclei produced during nuclear fission

  • Chain reaction - a series of nuclear fission events, with each one triggered by a neutron from a previous nuclear fission

  • Nuclear fusion - the combining of small nuclei at very high temperatures with the release of energy

Nuclear fission and fusion reactions can be modelled by pupils using modelling clay. Simple visual explanations can be drawn for each as simple comic strips based on such models.
Teacher tip

Equipment

None required.

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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Starter quiz

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6 Questions

Q1.
Which of the following particles are found in the nucleus of an atom?
electrons
Correct answer: protons
Correct answer: neutrons
Q2.
An isotope can be defined as …
Correct answer: an atom of the same element with a different number of neutrons.
an atom of a different element with the same number of neutrons.
an atom of the same element with a different number of protons.
Correct answer: an atom with the same atomic number but different mass number.
Q3.
What are the possible differences between substances that contain isotopes of the same element?
Correct answer: they have different masses
they have different chemical reactivities
Correct answer: some isotopes are more stable than others
there are no differences
Q4.
Which particle affects the stability of a nucleus, and what factors determine if a nucleus is stable or unstable?
protons affect the stability of a nucleus
Correct answer: neutrons affect the stability of a nucleus
a nucleus is stable with more protons than neutrons
Correct answer: a nucleus is stable when the neutron–to–proton ratio is balanced
Q5.
Which of these can be released during nuclear reactions such as nuclear decay?
Correct answer: alpha particles
Correct answer: beta particles
Correct answer: neutrons
light
Correct answer: energy
Q6.
Which of the following statements accurately describes the changes that occur in the nucleus during radioactive decay?
Decay always emits gamma rays with no change in the nucleus.
Correct answer: Decay can emit alpha/beta particles or gamma rays, changing atomic no/mass no.
Decay only emits particles, with no nucleus changes or energy release.

Exit quiz

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6 Questions

Q1.
What is nuclear fission?
Breaking down electrons into protons and neutrons.
Correct answer: Splitting a heavy nucleus into smaller nuclei, releasing energy.
Emitting radiation from a substance without changing the nucleus.
Combining two light nuclei to form a heavier nucleus.
Q2.
Which of the following nuclear equations could represent the fission of a uranium–235 nucleus?
An image in a quiz
Correct answer: Equation 1
Correct answer: Equation 2
Equation 3
Equation 4
Q3.
Put the following stages of fission in the correct order, starting with a uranium–235 nucleus (U–235) absorbing a neutron.
1 - A U–235 nucleus absorbs a neutron, becoming a U–236 nucleus.
2 - The U–236 nucleus is unstable and splits into two, smaller nuclei.
3 - As well as the smaller nuclei, 2 or 3 neutrons are released.
4 - Energy, in the form of gamma radiation, is also released.
5 - More U-235 atoms absorb the released neutrons.
6 - A chain reaction occurs when more U–235 nuclei split releasing more neutrons.
Q4.
What is the key difference between spontaneous fission and induced fission?
Spontaneous fission needs external triggers; induced happens by itself.
Induced fission occurs naturally; spontaneous requires a neutron to be absorbed.
Correct answer: Spontaneous fission occurs naturally; induced requires a neutron to be absorbed.
Both types of fission occur due to temperature changes and external triggers.
Q5.
What is nuclear fusion?
Breaking down electrons into protons and neutrons.
Splitting a heavy nucleus into smaller nuclei, releasing energy.
Emitting radiation from a substance without changing the nucleus.
Correct answer: Combining two light nuclei to form a heavier nucleus.
Q6.
Nuclear fusion powers stars by combining light nuclei, such as hydrogen, into heavier elements. Why isn’t nuclear fusion currently a viable method for generating electricity on Earth?
It is too dangerous, producing large amounts of harmful radiation.
It only works with special fuels not found on Earth.
Correct answer: It requires extremely high temperatures and pressure, hard to recreate on Earth.
It generates less energy than nuclear fission.