Chapter 26 - Particles Flashcards
Explain how nuclear fission can lead to a chain reaction [3 marks]
- Nucleus splits - Releasing neutrons - Which are absorbed by different uranium nuclei
Nuclear fission releases energy; explain the form that this energy takes [2 marks]
- Kinetic energy of particles - Of (fission) products / (daughter) nuclei / neutrons
The pressurised water acts as a coolant. It also acts as a moderator. What is the purpose of a moderator? [1 mark]
- To slow down neutrons
Suggest why Geiger and Marsden removed the air from the apparatus of the goil foil experiment (1)
- alpha has a small range in air
- alpha would not hit the gold leaf
- alpha would be deflected
- alpha would collide with the air {particles/molecules/RA}
- alpha would ionise the {air/ particles/molecules}
Describe Geiger and Marsden’s results (2)
- most went (straight) through
- (the paths of) a few were deflected at an acute/small angle
- (the paths of) very few were {deflected through an obtuse angle / backscattered};
Rutherford produced a model of the atom. Describe how Rutherford’s model explains Geiger and Marsden’s results. (4)
- Small nucleus
- Mostly empty space
- Because not many α deflected / because most α go straight through
- Positive nucleus
- which causes deflection of positive (or low mass) α
Describe what happens when nuclear fission of uranium occurs (3)
- neutron absorbed by (U) nucleus
- (U nucleus) splits;
- (producing 2) daughter nuclei;
- extra neutrons released;
The daugter nuclei move off with high speed. Name the type of energy that this gives them. (1)
- Kinetic
What start the fission process in a nuclear reactor (1)
- Free neutrons
After free neutrons start the fission process, what happens (2)
- Atoms producd then collide with other atoms
- causing the temperature to in the reactor to rise
What is the purpose of a moderator (3)
- Made of graphite or water
- Slows neutrons so that they can succesfully collide with uranium nuclei,
- to sustain the chain reaction
What is the purpose of control rods (2)
- Often made of boron
- Limit the rate of fission by absorbing excess neutrons
What gas is pumped through the reactor, and why (2)
- Carbon dioxide
- To carry away the heat generated
After carbon dioxide is pumped through, what are the final stages in a nuclear reactor (7)
- Gas then passed through a heat exchange
- Where it gives its energy to water
- This water is heated
- turns to steam
- which turns a turbine
- which turns a generator
- which produces electricity
