P2.7 Energy From The Nucleus Flashcards
When does nuclear fission occur?
When a stable isotope is struck by a neutron. The isotope absorbs the neutron, becomes unstable and splits apart, releasing large amounts of energy.
What isotopes undergo nuclear fission?
Uranium-235
Plutonium-239
What do you need for a chain reaction?
Neutrons
When fission occurs, what does it split into?
Daughter nuclei
Draw a chain reaction.
Look it up
What the danger with chain reactions?
They release a lot of energy very quickly and if it’s uncontrolled heat builds up and could explode.
How are neutrons controlled?
The reactors graphite core slows down released neutrons so chain reaction can keep going.
Control rods made of boron absorb excess neutrons to prevent chain reactions getting out of control.
Draw a reactor for nuclear fission.
Look it up
How does nuclear fission start?
A uranium-235 atom absorbs a low speed neutron
What are pros of nuclear fission?
Reduces use of fossil fuels
No greenhouse gases produced
Cheap to run once built
What are cons of nuclear fission?
Expensive to build new power stations
Produces long lasting nuclear waste
Risk of uncontrolled chain reactions.
What’s nuclear fusion?
Powers the sun and other stars.
Small nuclei join together to form larger nuclei and energy is released.
What are deuterium and tritium?
Isotopes of hydrogen
Deuterium + tritium ->
Fusion -> helium + neutron
What conditions does nuclear fusion happen in?
In stars
High temp
High pressure
What’s a life cycle for a star about the same size as our sun?
Protostar Main sequence star Red giant White dwarf Black dwarf
What’s the life cycle for a star bigger than our sun?
Protostar Main sequence star Red super giant Supernova Then either neutron star or a black hole
How do all stars start?
Nebula
Large clouds of dust and gas (mainly hydrogen)
Give details of a protostar
Over millions of years gravity will cause dust&gas in the nebulae to come together. As it does this the temperature increases until hydrogen can fuse. When this happens a protostar is born. This is a star nursery.
Give details of a main sequence star
Next stage after protostar. Hydrogen fusion has been happening and the star is much hotter and brighter than the protostar.
Give details of a red giant star
When a star runs out of hydrogen it begins to fuse other heavier elements. This releases more energy causing the star to expand. It also gives off red light, hence the name.
Give details of a white dwarf.
When the red giant runs out of fuel and can fuse nothing more it will lose its outer layers. This leaves just the core which is still extremely hot. It’s so hot it glows white hot giving its name.
Give details of a black dwarf.
After a long enough time the white dwarf will cool down enough so that it stops glowing white hot. Now called black dwarf.
Give details of a red super giant star
Following the main sequence the star begins to fuse together heavier elements. However, as it has far more fuel, it expands to a much larger size and gives off much more energy.
What can a red super giant star fuse? Why’s it significant?
Elements up to iron
Iron is the most stable element in the universe
Give details for a supernova
For very heavy stars, once they have run out of fuel, the star begins to collapse in on itself. It continues to collapse until it reaches a critical point when it can’t collapse anymore. This cause a massive shockwave. This naturally produces elements above iron. Outer layers expand outwards. Even though it lasts seconds, it’s the largest explosion known to man.
Give details for a neutron star.
After a supernova, only the stars core is left behind. During the collapsing process, this core is turned into just neutrons. The resulting neutron star is very very dense.
Give details on a black hole
In some very rare cases, the core of a star left over a supernova will co tinge to collapse. It will keeps getting smaller and smaller until the whole star has collapsed into an infinitely small point. It has an immense gravitational force, not even light can escape from it.
Why are lots of elements formed?
In stars
Does fission or fusion produce nuclear weapon materials?
Nuclear fission
Does fission or fusion use hydrogen isotopes?
Fusion
Does fission or fusion use an uranium isotope?
Fission
Why fission or fusion has a highly radioactive process?
Fission
Which out of fusion and fission is technically difficult?
Fusion
Which out of fusion and fission produces no radioactive waste?
Fusion
Which fission or fusion needs control rods for safety?
Fission
Which fission or fusion process powers the sun?
Fusion
