Energy From The Nuckeus Flashcards
Which fissionable isotopes are used?
Uranium- 235
Plutonium 239
What is the most naturally occurring form of uranium?
U-238, which is non fissionable
What is enriched uranium?
Uranium which contains 2-3% of fissionable U-235
What must happen for fission to occur?
The U- 235 or plutonium 239 nucleus must absorb a neutron. Then the nucleus splits into 2 smaller nuclei. In the process 2 or 3 more neutrons are emitted and energy is released
Why is nuclear fission better than burning?
Nuclear fission releases much more energy than burning
When does a chain reaction occur in nuclear fission?
When each fission event causes further fission events
How is the process of nuclear fission controlled?
Only one fission neutron per fission on average goes onto produce further fission
What is nuclear fusion?
The process of forcing 2 nuclei close enough together so they form a single larger nucleus
How can cycle at fusion be brought about?
Making 2 light nuclei collide at very high speed
Where does fusion occur naturally?
Stars
Why must the fusion nuclei by heated to a very high temperature?
To overcome the repulsion of the positive charge and force the nuclei to fuse
How are nuclei contained in a fusion reaction?
Contained in a magnetic field
What is the biggest source of background radiation
Radon gas which seeps through the ground from radioactive substances in rocks deep underground
Why is radon gas a health hazard?
Radon emits alpha particles so is a health hazard if breathed in
List other sources of background radiation
Cosmic rays from space, food and drink, air travel and nuclear weapons testing and medical sources eg X-rays
How can workers reduce the risk of exposure to nuclear radiation?
Keep away from source of radiation
Spend little time exposed
Shield themselves with concrete or lead
Why must radioactive wate be stored securely?
So it does not enter the environment
Why is uranium and plutonium chemically removed from used fuel rods?
The substances can be used again
When did the Big Bang occur?
13 billion or thousand million years ago
What was the universe at first?
A hot glowing ball of radiation
What happened in the first few minutes of the Big Bang?
The nuclei of the lightest elements formed
As the universe expanded over millions of years what happened?
The temperature fell and uncharged atoms were formed
What is nuclear fission?
Is the splitting of an atomic nucleus
What happened to the temperature of the universe as it expanded?
It decreased
Before galaxies and stars formed what was the universe like?
A dark patchy cloud of hydrogen and helium
What happened eventually so that starts were formed?
The dust and gas were pulled together by gravitational attraction to form stars
How did stars begin to emit light and radiation?
After the dust and gas was pulled together by gravitational attraction, the resulting heat started off nuclear fusion reactions in stars
What is a galaxy?
A very large group of stars held together by their own gravity
What is our galaxy called
The Milky Way
The distance between neighbouring stars is usually ………… Of times greater than the distance between………. In our solar system.
Millions
Planets
The distance between neighbouring ………… Is usually millions of times greater than the distance between …… Within a ……….
Galaxies
Stars
Galaxy
How are protostars formed?
Gravitational forces pull clouds of dust and gas together to form a protostar
The protostar becomes …….. And the nuclei of hydrogen atoms and other light elements start to ……. Together. Energy is released in the process so the core gets ……….. And ……….
Denser
Fuse
Hotter
Brighter
Why do stars radiate energy?
Hydrogen fusion in the core
Why are stars in the main sequence stage stable?
The inward force of gravity is balanced by the outward force of radiation from the core
What happens to a star when it runs out of hydrogen to fuse
It swells cools down and turn red
What type of star is the sun?
Red giant
What is the sequence that a low mass star will go through?
Protostar MSS Red giant White dwarf Black dwarf
When will a low mass star form a white dwarf?
When fusion stops the star will contract becoming a white dwarf
When will a low mass star form a black dwarf?
When no more light is emitted
After the main sequence a star much larger than pursue will become a…….
Red supergiant
What happens after a star is a red supergiant?
The star explodes in a supernova as the outer layers are thrown out into space?
What is the core of the star left after a supernova called
A neutron star
When does a neutron star become a black hole?
If it is massive enough
Why can no light escape from black hole.
The gravitational field strength is so strong
What is the heaviest element formed by fusion in stars
Iron
Why are elements heavier than iron only formed in the fink stages of the life of a big star?
The process requires an input of energy
What is the presence of heavier elements in the sun and innner planets evidence for.
They were formed from the debris scattered by. Supernova
Explain how stars like the Sun are thought to have been formed
Dust and gas or remnepants of
Explain how helium is formed in a star
Fusion of hydrogen
Explain how atoms of heavy elements were formed s
Fusion of light elements
During a supernova
Explain how and when different elements may be distributed throughout the universe
Supernova explosion
At the end of a stars life
Explain why scientists believe that the solar system was formed from the material produced when earlier stars exploded
Solar system contains heavy elements
Formed in a supernova
De scribe how a massive star bigger than the sun will change at the end of the main stable period
Expands into red giant
Explodes to become supernova
Dense neutron star left behind
If massive enough forms a black Hole
What is meant by the term black hole?
Matter with such high gravitational strength
Light is pulled in
Describe what happens to the sun as the hydrogen is used up until the sun dies u
fusion decreases or stops
• collapses rapidly causing the (core) temperature to rise
• (inward) gravitational forces no longer balance (outward) pressure
• expands
• and becomes a red giant
• it cools
• then becomes a white dwarf
Explain how our sun formed from the time when There was just dust and gas up to now when it is in the main sequence
Dust and gas pulled together Formed when it is hot enough Hydrogen fuses Releasing energy Which causes expansion Gravity is balanced to radiation pressure
