7 Fission and fusion Flashcards
What do nuclear reactions involve?
They involve a change in the qualities of atoms.
What is fission?
Heavy atoms may split into lighter atoms and other pieces in a process called fission.
What is fusion?
Lighter atom may be forced to join together to make heavier atoms in a process called fusion.
What happens in both fission and fusion, in relation to the mass of the products?
The mass of the starting atoms is greater than the mass of the products.
Where does this missing mass go?
It has been converted into energy.
What provides a large proportion of the heat within the Earth itself through radioactive decay?
Within the core of the earth, radioactive isotopes of elements like uranium, thorium and potassium provide this large proportion of heat.
Where is hydrogen converted into helium?
In the sun.
Through what process is hydrogen converted into helium?
In a fusion reaction.
What is a fusion reaction?
When the centers of atoms (nuclei) join together.
What does this fusion reaction provide us with?
It provides us with a continuous supply of energy in the form of heat and other electromagnetic radiation.
Why is uranium-235 used as fuel in a nuclear reactor?
It is used because its nuclei can be split by a neutron.
What is this process of splitting an atom called?
Fission.
What kind of material is uranium-235?
A fissile material.
Why is uranium-235 called a fissile material?
This is because it goes through the splitting process easily.
What happens in this fission reaction?
A slow-moving neutron is absorbed by a nucleus of uranium-235.
What is a diagram which shows an example of fission of uranium-235?
What happens to the resulting nucleus of uranium-236?
It is unstable and splits apart.
What are the fragments of this decay?
The fragments of this decay are the two daughter nuclei of barium-144 and krypton-89.
What else does the decay produce?
The decay also produces gamma radiation and three more neutrons.
What is the equation for this decay?
236 144 1
92 U –> 56 Ba + 3 0 n + γ radiation.
What does fission produce in terms of energy?
The fission reaction produces a huge amount of energy.
Why does fission produce a large amount fo energy?
This is because of the mass of the products, the barium and krypton nuclei and the three neutrons is slightly less than that of the original uranium-236 nuclei, and the lost mass is converted into energy.
Where does this energy go?
- Most of this energy is carried away as the kinetic energy of the two lighter nuclei.
- Some is emitted as gamma radiation.
What are the two reasons as to why the fission process would repeat?
- The three neutrons produced by the fission may hit other nuclei of uranium-235, so causing the process to repeat.
- if one neutron from each fission causes one nearby uranium-235 to split, then the fission reaction will keep going.