6188011
Description
Flashcards by Mel Hughes, updated more than 1 year ago
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Created by Mel Hughes
over 7 years ago
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| Question | Answer |
| What is enriched uranium? | Uranium that contains 2-3% uranium-235 |
| What happens for fission to occur? | A nucleus absorbs a neutron |
| By what process is energy released in stars? | Fusion |
| How are nuclei contained in a fusion reactor? | In a magnetic field |
| What is the major source of background radiation? | Radon gas |
| Why must radioactive waste be stored securely? | So that it does not enter the environment because it remains radioactive |
| What happened to the temperature of the universe as it expanded? | It decreased |
| What is a galaxy? | A collection of billions of stars held together by their own gravity |
| Why are stars in the main sequence stable? | The forces acting on them are balanced |
| What is a neutron star? | The core left after a supernova explodes |
| What is the heaviest element formed by fusion in a main sequence star? | Iron |
| How are the chemical elements distributed through space? | By a supernova explosion |
| What is a fissionable isotope? | An isotope that can undergo the process of fission |
| Which two fissionable isotopes are used in nuclear reactors? | Uranium -235 and plutonium -239 |
| When does a chain reaction occur? | When each fission event causes further fission events |
| What is nuclear fusion? | The process of forcing two nuclei close enough together so they form a single larger nucleus |
| How can nuclei be made to come close enough to fuse? | Nuclear fusion can be brought about by making two light nuclei collide at very high speed |
| How long did it take for the temperature of the universe to fall enough so that uncharged atoms were formed? | Millions of years |
| Why is a black hole black? | Not even light can escape from it |
| When is a black hole formed? | After a supernova, if the star has sufficient mass |
| What will the final stage in the life cycle of the Sun be? | A black dwarf |
| What evidence is there that the Sun and inner planets formed from the remnants of a supernova? | The presence of the heavier elements in the Sun and inner planets |
| What is the name of the process that produces the chemical elements? | Fusion |
| When are elements heavier than irons formed? | In a supernova |
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