Fission & Fusion
Give the formula for change in energy
ΔE = Δmc²
Explain einsteins hypothesis
Mass and energy were linked via the mass energy equivalence. Mass can be thought of as energy in the form of mass-energy
Which form of energy does the mass-energy equivalence apply to?
All forms of energy
Define 'Binding energy'
The minimum energy needed to separate a nucleus into its constituent components
Why is the mass a particle different to the mass of nucleons that make up the particle
That difference in energy goes into the binding energy of the particle
Define an antiparticle
Particle that have the same mass but different charge to another particle
Define 'Annihilation'
Where a particle meets an antiparticle and the entire mass of both are converted into energy(photons)
Define 'Mass Defect'
The difference between the mass of a nucleus and the nucleus completely separated
Define 'Nuclear Fission'
Where a large nucleus is split into smaller nuclei
Define 'Nuclear Fusion'
Where a two smaller nuclei are combined (fused) into one large nucleus
Give the formula for the binding energy per nucleon
ΔE/N(no of nucleons)
Explain the process of Fission
Unstable nuclei can either spontaneously split or a neutron is shot into them for it to split. The nuclei s then split into two smaller nuclei. In addition, two/three neutrons are emitted and also energy(photons) are emitted
How do power stations work
In the reactor tank, there's coolant and fuel rods. The fuelrods contain the unstable uranium, and the fission reactions occur in them. These rods release neutrons and energy, the neutrons cause chain reactions between the uranium in the rods, and the energy heats up the coolant causing steam. There are also moderators which slow down the speed of the neutrons so that they can get absorbed into the nuclei in the rods(if too fast, they won't get absorbed). The control rods control the amount of neutrons that get absorbed so that neither too little or too much steam is produced.
Fission reactors also produce radioactive products, what is done with this
They produce toxic waste (left over uranium is melted in acid) which is encased in glass and buried. Glass is non porous
Where does fusion happen and explain this process
In the sun. Unstable hydrogen nuclei are fused together, then undergo beta decay. These nuclei move very fast to overcome the electrostatic repulsion between them
In both fission and fusion, why does the binding energy increase
mass is lost in each of these processes
Finish the sentence, the more nucleons in a nucleus
The greater the binding energy(ONLY UP TO A NUCLEON NUMBER OF 56)
What happens when an atom has a lower or higher nucleon number than 56
Lower - The nulceus undergoes fusion to get closer 56 (increase its nucleon number)
Higher - The nulceus undergoes fission to get closer 56(decrease its nucleon number)
What does the small bump in the binding energy per nucleon graph represent
An alpha particle. It has an unusually higher stability in comparison to nuclei with a slightly higher/lower nucleon number
Why do nuclei need high amounts of KE during fusion
To overcome the electrostatic repulsion between protons.
Where is nuclear fusion most likely to occur?
In places with very high temperatures e.g. core of stars or places with high pressure.