Physics 3- The Earth, Stars and Elements

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What proof is there that the Big Bang created the universe?
Red Shift and CMBR (radiation)
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How were elements like deuterium originally formed?
As the universe cooled, protons and electrons combined, producing deuterium, which then combined to make helium and trace amounts of lithium
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By what process were the light elements formed?
Big Bang Nucleosynthesis
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What is the elemental composition of the Universe?
75% Hydrogen, 25% Helium and very small quantities of other elements.
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Where are all other elements created?
In stars
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How are 1st Generation stars composed?
mainly of hydrogen and helium, heavier elements are not synthesised yet
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What does SM stand for and what is it?
Solar masses and how big something compared to the sun e.g. 3 SM is the sun's volume x3
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What are the stages a star goes through to become a white dwarf?
A gravitational collapse of dust, gas and cloud (nebula)-Yellow star, up to 8 SM- Red giant stage (star is running out of hydrogen)- Planetary nebula- white dwarf
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How is a Neutron star formed?
Gravitational collapse of dust,gas and cloud (nebula)- Blue star (less than 8 SM)- Red super giant stage (star is running out of hydrogen)- Supernova explosion(heavier elements are formed)- Neutron star
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How is a black hole formed?
Same process as a neutron star, only if the star is big enough it will become a black hole
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What is the difference between the two processes?
Small stars become white dwarfs and larger stars become neutron stars/black holes
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What are brown dwarfs?
Failed stars, their mass isn't big enough to generate enough heat for nuclear fusion.
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What is a red dwarf star?
Low mass stars that do achieve nuclear fusion but are not very bright and have long lifetimes
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What kind of stars are red dwarfs?
Main sequence stars
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What are the forces acting in a star?
Inward force of gravity and outward force of gas/radiation pressure
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Describe the gas pressure?
Rapid, random motion of particles colliding
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Describe the radiation pressure?
Light hitting the particles
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In what state is a star in for most of its life and why?
The forces are balanced and so the star is stable
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What happens if the pressure in the middle of the star decreases?
The star shrinks, the pressure then rises until it balances again
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What happens if the middle pressure increases?
The star expands
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What is happening in the main sequence of a star's life?
Fusion of Hydrogen and Helium
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What does the colour of the star depend on?
The temperature
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What is the most common star?
Yellow star
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What happens at the end of the main sequence?
The hydrogen has run out, the star swells to a red giant- the temperature decreases as nuclear fusion stops.
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What happens to the forces of the star at the end of the main sequence?
The gravitational pressure is greater than the gas/radiation pressure
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What happens to the core at this point?
It shrinks
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What then happens?
Helium fusion starts, the temperature rises as does the gas and radiation pressure
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How is a white dwarf formed from the end of the main sequence?
Light elements within the star fuse, there are no light elements in the centre, nuclear reactions stop, the pressure decreases.
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And then?
The nucleas shrinks, the density and temperature increases, the heavier elements fuse.
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And then?
The lighter elements fuse in shells around nucleas, but hte temperature is never sufficient to fuse elements heavier than oxygen.
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And then?
The outer layer is pushed off by radiation pressure of core, enriching the interstella medium with heavier elements. The remaining very dense core is a white dwarf
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What is the purpose of fusion?
Mian sequence stars gain energy from the fusion of hydrogen and helium
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What is a positron?
An antiparticle of an electron
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Describe annhilation
When a particle and its corresponding particle meet
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What happens in annihilation?
Lots of energy is released, when a positron in produced in fusion it meets an electron and is annihilated
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What can mass potentially convert to?
Energy
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Describe fusion in stars bigger than the sun
It's more difficult to fuse heavier elements because heavier nuclei repel, a higher temperature is required
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Where is fusion of heavier elements isolated to happening?
Stars with a greater mass than the sun
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What are these stars like?
They have a shorter lifetime, using fuel quicker. Higher core temperature and the production of heavier elements happens in shells around nucleus (limit depends on mass/temp)
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What happens when the fusion source is exhausted?
Core collapsing causing a supernova explosion making a neutron star or a black hole
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How dense is a neutron star?
Very dense
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When fusion stops, what happens to make the core collapse?
The gravitational force becomes too much
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What happens in a supernova explosion?
Much of the heavier elements are blasted into space to become new stars in the interstella space. As the shock encounters material in outer layers, greatly heated and fuses to heavier elements
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What elements are formed in a supernova explosion?
Elements heavier than iron and nickel
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What does a higher binding energy figure mean about the nucleus?
It's more stable
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What is at the peak of the binding energy curve?
Iron group, anything above that value drastically absorbs energy
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What happens to heavy stars when producing iron and nickel?
They run out of energy and die in a supernova, the extra energy released produces heavier elements , which are blasted into space to form the gas/dust/cloud of a new solar system
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Where are most atoms in the body formed?
In a supernova explosion
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Define Nuclear fission?
The decaying of an unstable nucleus into 2 fragments of lighter nuclei/comparable mass
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What are the new nuclei's properties?
Higher binding energy per nucleus than original element
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What does a higher binding energy value result in?
More energy is released
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Why are you only able to use elements such as uranium in a fission reactor?
The element was released by a supernova form a gravitational collapse of a huge star
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What are the most common elements?
Hydrogen and helium, then oxygen and iron
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Generally, what does a decrease in abundance of elements show?
A higher proton number
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Why should you expect a decrease in the abundance of elements heavier than oxygen?
They are formed in a supernova explosion
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How can the abundance oxygen and carbon be explained?
Scientific research
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What did Fred Hoyle use and what did he find?
Experimental results to show how heavy elements could be produced and why some were more common
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What is an example of a theory proved by experimental results?
The production of Nitrogen, Oxygen and Carbon
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What is the process for a scientific finding?
Observation, Theory and experimental proof.
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Other cards in this set

Card 2

Front

How were elements like deuterium originally formed?

Back

As the universe cooled, protons and electrons combined, producing deuterium, which then combined to make helium and trace amounts of lithium

Card 3

Front

By what process were the light elements formed?

Back

Preview of the front of card 3

Card 4

Front

What is the elemental composition of the Universe?

Back

Preview of the front of card 4

Card 5

Front

Where are all other elements created?

Back

Preview of the front of card 5
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