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| Question | Answer |
| what is nuclear fission? | Nuclear fission is the SPLITTING of an atomic nucleus |
| what is nuclear FUSION? | the joining of two atomic nuclei to form a larger one |
| what are the two fissionable substances in common use in nuclear reactors? | uranium 235 and plutonium 239 |
| what must happen to the radioactive atom before fission can occur? | the nucleus must first absorb a neutron |
| what happens to the nucleus undergoing fission? | the addition of the neutron makes the nucleus unstable causing it to split. the nucleus undergoing fission splits into two smaller nuclei and two or three neutrons and energy is released. |
| what is a chain reaction? |
Image:
fission (image/png)
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| how is energy released in stars? | by nuclear fusion |
| what conditions are needed for stars to form? | enough dust and gas from space is pulled together by gravitational attraction. |
| how are planets formed? | smaller than stars, masses may form and be attracted to a larger mass to become planets |
| why is a star stable during the 'main sequence' period of its life | the forces within it are balanced |
| a stars life cycle is determined by what? | its size |
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