NUCLEAR FISSION Flashcards
WHAT IS NUCLEAR FISSION
Splitting of an atomic nucleus.
The nucleus absorbs a neutron and then splits into two smaller nuclei. In the process 2 or 3 neutrons are emitted, which causes fission to go on further. Energy is released in greater quantities.
WHAT IS A CHAIN REACTION?
When each fission causes further fission events.
WHAT IS NUCLEAR FUSION?
The process of forcing 2 nuclei close together so they form a single larger nucleus.
For fission to occur they force of repulsion must be overcome so the nuclei can get close enough to fuse.
The nuclei must collide at a very high speed
Eg. In stars hydrogen nuclei fuse to make a helium nucleus.
FORMATION OF SUN SIZED STARS.
NEBULA a large cloud of gas and dust, which gravity forces to collapse in on itself, forming a
PROTOSTAR which has a very hot and dense centre, when the temperature is hot enough and the pressure is dense enough nuclear fission starts and it becomes a
MAIN SEQUENCE STAR which is where the sun currently is. Nuclear fusion of hydrogen and helium is taking place and the gravitational force in .is balanced with the radiation force out. It expands into a
RED GIANT where the nuclear fusion of helium into carbon and oxygen takes place. When it runs out of hydrogen core collapses. Core hears up and fusion of helium and larger elements take place. This releases more energy and the outer layers are blown away.
It forms a hot and dense WHITE DWARF
which when fusion stops contracts and cools to a BLACK DWARF
FORMATION OF STARS LARGER THAN THE SUN
Nebula ; Protostar ; Main Sequence ; Red Super Giant ; Super Nova ; Neutron Star ; Black Hole
WHAT IS A SUPER NOVA?
WHAT IS A RED SUPER GIANT?
Fusion stops and the star collapses in on itself. A massive explosion that flings the outer parts into space - leaving behind a dense core. This is how all the heaviest elements are distributed.
A red super giant is where the fusion of helium into carbon oxygen and heavy elements all the way to iron.
WHAT IS A NEUTRON STAR?
WHAT IS A BLACK HOLE ?
They are extremely dense, with a mass greater than the sun.
Black holes are so dense not even light can escape.
