Fission and fusion
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 4 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Two ways to release nuclear energy
- Nuclear fission
- A fission equation
Read the transcript of the teaching part
Last time
Before we start: last time, in Detecting radiation, background and uses of isotopes, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Two ways to release nuclear energy
A nuclear power station and the Sun both release energy from the nucleus. One does it by splitting heavy nuclei. The other does it by joining light nuclei together. A tiny mass of fuel gives a huge amount of energy, millions of times more than burning coal.
Nuclear fission
In fission, a large, unstable nucleus splits into two smaller nuclei, called daughter nuclei, and releases energy. It also releases two or three neutrons. The energy is carried away by the daughter nuclei as kinetic energy. The fuel is uranium-235 or plutonium-239.
A fission equation
A uranium-235 nucleus absorbs a neutron, splits into barium-141 and krypton-92, and releases 3 neutrons. The nucleon numbers balance: 235 plus 1 is 236, and 141 plus 92 plus 3 is also 236. The proton numbers balance too: 92 equals 56 plus 36.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Fission and fusion.
The whole chapter: Radioactivity, Radioactivity.
Chapter 5.2: Radioactivity
- Alpha, beta and gamma radiation 6 min
- Detecting radiation, background and uses of isotopes 6 min
- Decay equations and half-life 6 min
- Fission and fusion 6 min
Also for O Level Physics 5054
Which topics come up most in O Level Physics 5054 past papers, counted from every paper since 2004.