Nucular fussion & fission

• What is the force which pulls the dust and gas together?


  Gravitational
• The smaller masses may be attracted by the star and become Planets
• Our nearest star, the Sun, is stable because the gravitational forces and the radiation pressure are equal
• Describe what happens to the nucleus of an atom during nuclear fission

  It splits into smaller parts and neutrons are emitted
• Nuclear fusion


  the nuclei of two atoms joining together
• Nuclear fission

  the nucleus of an atom splitting into several pieces
• Ionisation

  an atom losing an electron
• Electric current


  an electric charge moving through a metal
• Explain briefly how stars like the Sun are thought to have been formed.

  -Dust and gas pulled together by gravity

  -nuclear fusion starts
• Describe the process of nuclear fusion.

  Two nuclei join forming a larger nuclei
• Where does nuclear fusion happen naturally?

  Star
• Explain briefly the difference between nuclear fission and nuclear fusion

  fission is the splitting of a nucleus

  fusion is the joining of nuclei
• What is released during both nuclear fission and nuclear fusion?

  Energy
• Stars are stable during the ‘main sequence’ period of the life cycle. Why?

  Forces are balanced
• Describe what happens to a star much bigger than the Sun, once the star reaches the end of the ‘main sequence’ period of its life cycle.

  Gravitational force balanced by radiation pressure
• Describe what happens to a star much bigger than the Sun, once the star reaches the end of the ‘main sequence’ period of its life cycle.


  star runs out of hydrogen and expands and cools forming a red super giant which explodes as a supernova becoming a neutron star
• Shortly after the ‘big bang’, hydrogen was the only element in the Universe. Explain how the other elements came to be formed.

  By fusion of hydrogen to helium and elements heavier than iron are only produced in a supernova
• Explain why the Sun remains stable.

  Gravity and radiation pressure in the correct direction of forces are balanced
• What happens to the elements produced in a supernova?

  Distributed throughout the Universe
• Explain the difference between a protostar and a main sequence star.

  A protostar is at a lower temperature as fusion hasn’t started
• Energy is released from nuclear fuels by the process of nuclear fission. This energy is used to generate electricity. Describe how this energy is used to generate electricity

  used to heat and water to produce steam which drives a turbine
• Explain the advantages of using energy from nuclear fuels to generate electricity rather than using energy from the wind.

  Concentrated source of energy that’s able to generate continuously the energy from fission is used to heat water to steam to turn a turbine linked to a generator
• Describe how 'carbon capture' would prevent the build-up of carbon dioxide in the atmosphere.

  carbon dioxide is not released but is stored             
• Explain how atoms of very heavy elements, such as gold (Au), were formed.

  Fusion of other elements during a supernova

   
• electrical forces inside a nucleus contribute to nuclear

  instability
• uranium-235, uranium-238 and uranium-239 are different


  isotopes
• nuclear fission occurs when

  electrical forces inside a nucleus overpower nuclear forces
• when U-235 splits, it usually emits

  three neutrons
• most nuclear power reactors work by

  boiling water, generating heat, running turbines, producing steam
• besides U-235, another material that undergoes fission readily is


  plutonium-239
• a benefit to using nuclear fission power is that it

  supplies a lot of electricity, conserves organic fuels, like oil, coal and wood, eleiminates huge quantifies of sulfur oxides, which pollute our air
• the release of energy in nuclear fission is consistent with the fact that uranium has


  more mas per nucleon than either of the two fragments
• a breeder reactor is more efficient than a convertional nuclear fission reactor in that


  nuclear fuel is created inside the reactor, unfissionable material is converted into fissionable material, there is plentiful supply of material for itSee an expert-written answer!We have an expert-written solution to this problem!
• in a breeder reactor

  uranium is converted into plutonium
• reactions that take place in a breeder reactor primarily change

  elements into different elements
• in gaseous form at the same temperature, the average speed of U-238 compared to the speed of U-235 is

  less
• compared to a neutron bouncing off a gold nucleus, a neutron bouncing off hydrogen nucleus has

  less speed
• a mass spectrograph separates ions by using


  a magnetic field
• a graph of nuclear mass per nucleon for all the elements


  starts high, dips, the slowly increases
• the element with the least mass per nucleon is


  iron