6-Fission & Fusion Flashcards
Why does a star remain stable?
There are balanced forces within it-mainly pressure of fusion creating an explosive outwards force and the force of gravity acting inwards.
How are stars formed?
- Gravitational attraction pulls clouds of gas and dust (nebulae) together to form a protostar.
- As it comes together it gets hotter. Eventually it’s hot enough for hydrogen to fuse into helium and a star is formed. The fusion produces massive amounts of energy.
- Dust may also clump together to form larger masses and eventually planets.
What is a star called when the forces are balanced?
A main sequence star.
What is the life cycle of a star the size of our sun?
Expands to become red giant.
Red giant cools and collapses under its own gravity to become a white dwarf.
White dwarf slowly cools to become black dwarf.
What is the life cycle of a star much bigger than our sun?
Expand enormously to become red supergiants.
Ted supergiant shrinks rapidly and explodes releasing a lot of energy, dust and gas into space. This is a supernova.
The remains may form a neutron star which is the core of the star that remains.
It may also form a black hole by a large neutron star collapsing.
What is nuclear fusion?
The joining of two or more atomic nuclei to form a larger atomic nucleus.
Why is nuclear fusion self-sustaining?
It generally releases more energy than it uses.
How do two heavy forms of hydrogen (deuterium and tritium) fuse together during nuclear fusion?
The nuclei fuse together to form a new helium atom and an unchanged neutron.
What is nuclear fission?
The process of splitting large atomic nuclei.
How does nuclear fission work?
The nucleus absorbs a neutron.
The nucleus slits into two smaller nuclei emitting two or three neutrons and releasing energy.
These neutrons can be absorbed by other nuclei causing a chain reaction.
