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Lamda > Energy From The Nuckeus > Flashcards

Energy From The Nuckeus Flashcards

1
Q

Which fissionable isotopes are used?

A

Uranium- 235

Plutonium 239

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2
Q

What is the most naturally occurring form of uranium?

A

U-238, which is non fissionable

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3
Q

What is enriched uranium?

A

Uranium which contains 2-3% of fissionable U-235

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4
Q

What must happen for fission to occur?

A

The U- 235 or plutonium 239 nucleus must absorb a neutron. Then the nucleus splits into 2 smaller nuclei. In the process 2 or 3 more neutrons are emitted and energy is released

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5
Q

Why is nuclear fission better than burning?

A

Nuclear fission releases much more energy than burning

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6
Q

When does a chain reaction occur in nuclear fission?

A

When each fission event causes further fission events

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7
Q

How is the process of nuclear fission controlled?

A

Only one fission neutron per fission on average goes onto produce further fission

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8
Q

What is nuclear fusion?

A

The process of forcing 2 nuclei close enough together so they form a single larger nucleus

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9
Q

How can cycle at fusion be brought about?

A

Making 2 light nuclei collide at very high speed

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10
Q

Where does fusion occur naturally?

A

Stars

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11
Q

Why must the fusion nuclei by heated to a very high temperature?

A

To overcome the repulsion of the positive charge and force the nuclei to fuse

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12
Q

How are nuclei contained in a fusion reaction?

A

Contained in a magnetic field

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13
Q

What is the biggest source of background radiation

A

Radon gas which seeps through the ground from radioactive substances in rocks deep underground

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14
Q

Why is radon gas a health hazard?

A

Radon emits alpha particles so is a health hazard if breathed in

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15
Q

List other sources of background radiation

A

Cosmic rays from space, food and drink, air travel and nuclear weapons testing and medical sources eg X-rays

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16
Q

How can workers reduce the risk of exposure to nuclear radiation?

A

Keep away from source of radiation
Spend little time exposed
Shield themselves with concrete or lead

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17
Q

Why must radioactive wate be stored securely?

A

So it does not enter the environment

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18
Q

Why is uranium and plutonium chemically removed from used fuel rods?

A

The substances can be used again

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19
Q

When did the Big Bang occur?

A

13 billion or thousand million years ago

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20
Q

What was the universe at first?

A

A hot glowing ball of radiation

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21
Q

What happened in the first few minutes of the Big Bang?

A

The nuclei of the lightest elements formed

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22
Q

As the universe expanded over millions of years what happened?

A

The temperature fell and uncharged atoms were formed

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23
Q

What is nuclear fission?

A

Is the splitting of an atomic nucleus

24
Q

What happened to the temperature of the universe as it expanded?

A

It decreased

25
Q

Before galaxies and stars formed what was the universe like?

A

A dark patchy cloud of hydrogen and helium

26
Q

What happened eventually so that starts were formed?

A

The dust and gas were pulled together by gravitational attraction to form stars

27
Q

How did stars begin to emit light and radiation?

A

After the dust and gas was pulled together by gravitational attraction, the resulting heat started off nuclear fusion reactions in stars

28
Q

What is a galaxy?

A

A very large group of stars held together by their own gravity

29
Q

What is our galaxy called

A

The Milky Way

30
Q

The distance between neighbouring stars is usually ………… Of times greater than the distance between………. In our solar system.

A

Millions

Planets

31
Q

The distance between neighbouring ………… Is usually millions of times greater than the distance between …… Within a ……….

A

Galaxies
Stars
Galaxy

32
Q

How are protostars formed?

A

Gravitational forces pull clouds of dust and gas together to form a protostar

33
Q

The protostar becomes …….. And the nuclei of hydrogen atoms and other light elements start to ……. Together. Energy is released in the process so the core gets ……….. And ……….

A

Denser
Fuse
Hotter
Brighter

34
Q

Why do stars radiate energy?

A

Hydrogen fusion in the core

35
Q

Why are stars in the main sequence stage stable?

A

The inward force of gravity is balanced by the outward force of radiation from the core

36
Q

What happens to a star when it runs out of hydrogen to fuse

A

It swells cools down and turn red

37
Q

What type of star is the sun?

A

Red giant

38
Q

What is the sequence that a low mass star will go through?

A 
Protostar
MSS
Red giant
White dwarf
Black dwarf
39
Q

When will a low mass star form a white dwarf?

A

When fusion stops the star will contract becoming a white dwarf

40
Q

When will a low mass star form a black dwarf?

A

When no more light is emitted

41
Q

After the main sequence a star much larger than pursue will become a…….

A

Red supergiant

42
Q

What happens after a star is a red supergiant?

A

The star explodes in a supernova as the outer layers are thrown out into space?

43
Q

What is the core of the star left after a supernova called

A

A neutron star

44
Q

When does a neutron star become a black hole?

A

If it is massive enough

45
Q

Why can no light escape from black hole.

A

The gravitational field strength is so strong

46
Q

What is the heaviest element formed by fusion in stars

A

Iron

47
Q

Why are elements heavier than iron only formed in the fink stages of the life of a big star?

A

The process requires an input of energy

48
Q

What is the presence of heavier elements in the sun and innner planets evidence for.

A

They were formed from the debris scattered by. Supernova

49
Q

Explain how stars like the Sun are thought to have been formed

A

Dust and gas or remnepants of

50
Q

Explain how helium is formed in a star

A

Fusion of hydrogen

51
Q

Explain how atoms of heavy elements were formed s

A

Fusion of light elements

During a supernova

52
Q

Explain how and when different elements may be distributed throughout the universe

A

Supernova explosion

At the end of a stars life

53
Q

Explain why scientists believe that the solar system was formed from the material produced when earlier stars exploded

A

Solar system contains heavy elements

Formed in a supernova

54
Q

De scribe how a massive star bigger than the sun will change at the end of the main stable period

A

Expands into red giant
Explodes to become supernova
Dense neutron star left behind
If massive enough forms a black Hole

55
Q

What is meant by the term black hole?

A

Matter with such high gravitational strength

Light is pulled in

56
Q

Describe what happens to the sun as the hydrogen is used up until the sun dies u

A

fusion decreases or stops
• collapses rapidly causing the (core) temperature to rise
• (inward) gravitational forces no longer balance (outward) pressure
• expands
• and becomes a red giant
• it cools
• then becomes a white dwarf

57
Q

Explain how our sun formed from the time when There was just dust and gas up to now when it is in the main sequence

A 
Dust and gas pulled together
Formed when it is hot enough
Hydrogen fuses
Releasing energy 
Which causes expansion 
Gravity is balanced to radiation pressure

Lamda (4 decks)

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