Production of Elements (Oxford AQA IGCSE Physics)
Revision Note
Production of Elements
Fusion reactions in stars are their source of energy
They produce all of the naturally occurring elements in the Universe
These elements may be distributed throughout the Universe by the explosion of a massive star (supernova) at the end of its life
For main sequence stars with a mass larger than that of our Sun:
Hydrogen nuclei combine in nuclear fusion reactions to produce helium nuclei, releasing lots of energy in the process
Stars maintain their energy output for millions of years because of the large amounts of hydrogen available
Once all of the hydrogen has reacted, fusion slows and the star expands becoming a red supergiant
Helium nuclei are then fused to form carbon
Further fusion processes take place in which heavier nuclei are formed such as nitrogen and oxygen
Heavier elements up to iron are also formed
Forces on a main sequence star
Once the fusion reactions inside the red supergiant cannot continue, the core of the star will collapse suddenly
The outer layers are blown away in a gigantic explosion
This is called a supernova
The temperatures in the explosion are so high that the heavier nuclei can fuse to create all the naturally occurring elements in the Universe
All elements heavier than iron are created in supernovae
The explosion disperses these elements out into space
The early Universe contained only hydrogen because fusion is needed to create heavier nuclei
Before stars formed there was no fusion
Forces on a red supergiant
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