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Physics P2 > Fission, Fusion and Stars > Flashcards

Fission, Fusion and Stars Flashcards

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1
Q

What is the basic idea of nuclear fission?

A

The splitting up of big atomic nuclei

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2
Q

What is the basic idea of nuclear fusion?

A

The joinging up of small atomic nuclei

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3
Q

Fission: What do nuclear power stations generate electricity using?

A

Nuclear reactors

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4
Q

Fission: What takes place inside a nuclear reactor?

What happens in this process?

A

A controlled chain reaction

Atomic nuclei split up an release energy in the form of heat

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5
Q

Fission: What happens to the heat generated in a nuclear reactor from the splitting up of atomic nuclei?

A

It is used to heat water to make steam which drives a steam turbine which is connected to an electricity generator

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6
Q

Fission: What is the fuel used in the reactor? 1. usually… 2. sometimes…

A
  1. Uranium-235

2. Plutonium-239

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7
Q

Fission: Describe the diagram of the nuclear fission reactor…

  1. Reaction chamber
  2. Steam area
  3. Bottom tube
A
  1. Coolant rods stick into the vat and uranium fuel rods are inside, in water.
  2. The heated water moves along a tube to the second vat through a series of pipes, the water around these pipes is heated and steam is released up a tube to the generator.
  3. The steam returns as water through a tube back into the vat and goes along a bottom tube as a pressurized coolant, to the coolant pump, then back into vat 1.
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8
Q

Fission: What happens in the first step of the chain reaction?
1. What happens……… this makes it … causing it to ….

A
  1. A slow moving neutron must be absorbed into the uranium nucleus. This extra neutron makes the nucleus unstable causing it to split.
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9
Q

Fission: What happens every time a uranium or plutonium nucleus is split?
2. When split….. . These might ….. This causes the…

A
  1. Two or three neutrons are spit out, one of which might hit another nucleus causing that one to split, so the chain reaction continues….
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10
Q

Fission: After a large atoms splits into two smaller …. these are what…. because they…..?

A

nuclei, radioactive, wrong number of neutrons in them

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11
Q

Fission: What are nuclear bombs more powerful than normal chemical bombs?

A

A nucleus splitting up releases a lot more energy than a chemical reaction.

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12
Q

Fission: What is the main problem with nuclear power?

Why?

A

The disposal of the waste

It is very radioactive, so it is difficult and expensive to dispose of safely.

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13
Q

Fission: What is cheap?

What is expensive and why?

A

The fuel
The overall cost of the plant because of the cost of the plant itself and the final decommissioning safely takes decades.

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14
Q

Fission: What do nuclear power plants also carry the risk of?

A

Radiation leaks or a major catastrophe like Chernobyl.

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15
Q

What is nuclear fusion in terms of nuclei?

A

Two light nuclei join to create a larger nucleus

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16
Q

Describe the diagram showing nuclear fusion:

  1. What comes together
  2. What this releases
  3. The other thing it releases
A
  1. H (one neutron, one proton) and H (one proton) come together and ‘fuse’
  2. Releasing He (two protons one neutron)
  3. and energy
17
Q

Fusion: Why are people trying to develop fusion reactors to generate electricity?
Why is it better than …?
Why is it a good method of electricity generation?

A

It releases a lot more energy than fission for a given mass.
Fission: because it doesn’t leave radioactive waste
There is lots of hydrogen to use as fuel

18
Q

Fusion: What is the one main problem?

What is the problem with the hydrogen under the required conditions? So you need a …

A

It requires really high temperatures of about 10,000,000 °C (10 million degrees)
You can’t hold it under this heat and large pressure required for fusion in normal containers so you need an extremely strong magnetic field.

19
Q

What is the current situation with fusion reactors?

  1. How many are there?
  2. What are they not doing?
  3. What is their problem?
A
  1. A few experimental reactors
  2. Generating electricity
  3. They take more power to get up to the temperatures required than they make through fusion.
20
Q

What are the two main journeys stars go through?

  1. 5 stars - big bright journey
  2. 4-5 stars- Darker journey
A
  1. Protostar, main sequence star, Red Super Giant, Supernova, Neutron star or a black hole
  2. Protostar, main sequence star, Red Giant, White Dwarf, eventually a black dwarf
21
Q
  1. How is a protostar formed?
    - What are they made of?
    - How do these come together?
A

From dust and gas.

The force of gravity makes these spiral in together to form the star

22
Q
  1. What happens after the protostar is formed but before it becomes a main sequence star?
    - What happens to the conditions?
    - What happens to the nuclei
    - How are planets formed
A

Gravitational energy is converted into heat energy and the temperature rises
When it gets hot enough hydrogen nuclei undergo nuclear fusion to form helium nuclei and give out massive amounts of light and heat - the star is born
Smaller masses of gas and dust may pull together to form planets that orbit the star

23
Q
  1. Main sequence star
    - When fusion begins what begins for the star? where what?
    - How long does the star remain in this stage and why?
    - How far through is our sun and what will happen to us at the end?
A

A long stable period where the heat released by fusion provides an outward pressure enough to counter gravity pulling everything inwards
The star maintains this energy output for several billion of years due to the massive amounts of hydrogen it consumes
Half way, we will be engulfed

24
Q
  1. Red Giant and Red Super Giant
    - What happens to make the change?
    - What is then formed?
    - What happens to the star itself?
    - Why does it become red?
A

Hydrogen starts to run out
Heavier elements such as iron are made by the nuclear fusion of helium
It swells into a Red Giant if its small or a Red Super Giant if it’s big
Its surface cools

25
Q
  1. After a Red Super Giant, SUPERNOVA.
    - What happens to make them get brighter again?
    - What is formed?
    - What then happens to the star? spewing what?
A

Big stars do this because they undergo more fusion and expand and contract several times
Elements as heavy as iron are formed in various nuclear reactions
It explodes in a super nova forming elements heavier than iron and ejecting them into the universe to form new planets and stars.

26
Q
  1. After a supernova, Neutron Star
    - How is it formed in relation to the supernova?
  2. After a supernova, Black Hole
    - Why is it sometimes formed instead of a neutron star?
A

The exploding supernova throws the outer layers of gas and dust into space leaving a very dense core - the star
If the star is big enough it will become a black hole

Physics P2 (11 decks)

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