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GCSE Physics > 6) Radioactivity > Flashcards

6) Radioactivity Flashcards

1
Q

What is the mass of positrons?

A

The same mass as electrons

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2
Q

Who discovered the nucleus?

A

Rutherford

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3
Q

What did Rutherford conclude?

A

A positively charged mass in the centre of an atom repelled particles

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4
Q

What did Rutherford fire?

A

Alpha particles

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5
Q

What happens when atoms absorb EM radiation?

A

Electrons move to a higher energy level further from the nucleus

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6
Q

What happens when atoms emit EM radiation?

A

Electrons drop to a lower energy level closer to the nucleus

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7
Q

What is the proton number (Z)?

A

Total number of protons

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8
Q

What is the nucleon number (A)?

A

Total number of protons and neutrons

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9
Q

What are the isotopes of hydrogen?

A

Protium
Deuterium
Tritium

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10
Q

What are specific isotopes of an element called?

A

Nuclides

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11
Q

How does an unstable nucelus become more stable over time?

A

By randomly emitting ionising radiation

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12
Q

What is the process of randomly emitting ionising radiation called?

A

Radioactive decay

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13
Q

How often is decay?

A

Decay is spontaneous

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14
Q

What are the 3 types of ionising radiation?

A

Alpha
Beta
Gamma

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15
Q

When does gamma radiation happen?

A

When an excited nucleus releases energy

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16
Q

How is gamma radiation produced?

A

By gamma decay

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17
Q

What does a neutron decay to form in beta-minus decay?

A

A proton and electron

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18
Q

What does a proton decay to form in beta-plus decay?

A

A neutron and positron

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19
Q

What happens to the products of beta decay?

A

They are ejected from the nucleus

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20
Q

What does alpha radiation release?

A

Helium nuclei (alpha particles)

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21
Q

What does alpha radiation do to the mass of the nucleus?

A

Decreases by 4 atomic units (2 protons and 2 neutrons)

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22
Q

How can radioactivity be detected?

A

Photographic film
Geiger-Muller tube
Cloud chamber

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23
Q

How do photographic films show radiation?

A

A bright spot appears where ionising radiation hits the film

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24
Q

How does a cloud chamber show radiation?

A

A chamber full of alcohol vapour condenses on ionising radiation leaving a trail of radiation

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25
Q

How does a Geiger-Muller tube show radiation?

A

1) Radiation enters tube full of low pressure gases
2) It ionises atoms in gas, knocking electrons out of atoms
3) Gas can now conduct electricity and completes an electric circuit
4) Current produces clicking noise
5) Count-rate is number of decays recorded each second

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26
Q

What are beta particles?

A

Electrons

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27
Q

How ionising are alpha particles?

A

Highly ionising but easily stopped (paper)

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28
Q

How ionising is beta radiation?

A

Fairly ionising but stopped by aluminium foil

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29
Q

What is beta plus radiation the emission of?

A

A positron

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30
Q

What is beta minus radiation the emission of?

A

An electron

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31
Q

How ionising is gamma radiation?

A

Weakly ionising but only stopped by centimetres of lead or concrete

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32
Q

What is gamma radiation used for?

A

Sterilisation

Exploring internal organs

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33
Q

How is gamma radiation used to explore internal organs?

A

We can trace radiation’s weakly ionising movement around the body
Gamma radiation has a short-half life meaning the radiation vanishes quickly

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34
Q

What is alpha radiation used for?

A

Smoke detectors

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35
Q

How is alpha radiation ued in smoke detectors?

A

1) Radioactive material fires alpha aprticles at smoke detector
2) If smoke comes bwteen radioactive material and smoke detecotr, less alpha particles reach detector setting off smoke alarm

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36
Q

What is beta radiation used for?

A

Paper production

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37
Q

How is beta radiation used in paper production?

A

1) Beta particles are fired through paper to make sure it is the right thickness
2) If thickness changes more or less beta particles reach detector stopping production

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38
Q

What is the most penetrating type of radiation?

A

Gamma

39
Q

How does nuclear fission happen?

A

1) Neutron collides with large nucleus and is absorbed, creating an unstable nucleus
2) Nucleus splits into fragments releasing energy and more neutrons
3) These neutrons then collide with other nuclei
4) Energy released is used to boil water which rotates a turbine which turns a generator, producing electricity

40
Q

What is the most common fuel soruce of nuclear fission?

A

Uranium-235

41
Q

Where does nuclear fission usually happen?

A

Nuclear reactors

42
Q

What do moderators control?

A

The speed at which neutrons travel in a reactor

43
Q

How does speed of neutrons affect nuclear fission?

A

Slower moving neutrons are more likely to trigger a fission reaction

44
Q

What do control rods control?

A

The number of neutrons in a reactor

They absorb neutrons to slow the rate of reaction

45
Q

How does removing control rods affect the rate of reaction?

A

Rate of reaction increases

46
Q

What uses the chain reactions of nuclear fission to create explosions?

A

Atom bombs

47
Q

What happens in nuclear fusion?

A

Two small nuclei are fused together to create a larger nucleus

48
Q

How do stars generate their energy?

A

Through the fusion of hydrogen and helium nuclei

49
Q

Why can’t scientists create sustainable energy using nuclear fusion?

A

Hydrogen must be heated to over 100 million degrees C

50
Q

What does nuclear fusion require?

A

Very high temperatures and pressure`

51
Q

What must be the same on each side when writing nuclear equations?

A

Atomic number

Mass number

52
Q

How does the element change in gamma decay?

A

The element does not change

0 protons or neutrons are lost

53
Q

How does the element change if nuclear fusion?

A

Protons remain the same

4 nucleons are relseased for chain reactions

54
Q

What does 1 atom decay to form in nuclear fission?

A

2 new atoms

Some neutrons

55
Q

What happens in beta decay?

A

A neutron decays to form an electron and a proton

56
Q

How does the element change in alpha decay?

A

4 nucleons are lost in the form of an alpha particle

2 protons are lost so the intial atom becomes a different element

57
Q

What does electrons being ‘excited’ mean?

A

They absorb energy and rise to a higher energy level

58
Q

What happens if electrons are excited enough?

A

They can escape the atom

59
Q

What happens if electrons are not excited enough?

A

They de-excite and emit radiation to lose energy

60
Q

What does ultraviolet absorbed by oxygen produce?

A

Ozone

61
Q

How are X-rays, UV and visible light generated?

A

When electrons in atoms lose energy and change their state in the atom

62
Q

What is emitted from the nucleus of atoms when the structure of the nucleus changes?

A

Gamma rays

63
Q

What is the process of an atom losing one of its outer electrons called?

A

Ionisation

64
Q

What can ionising radiation do?

A

Break molecules into small particles called ions

65
Q

What does cell damage from ionising radiation cause?

A

Mutations leading to cancer and organ failure

66
Q

What is the process of scientists checking each other’s work called?

A

Peer review

67
Q

What is a half-life?

A

The average time taken for the number of radioactive nuclei to halve

68
Q

What is the activity of a radioactive substance measured in?

A

Becquerels (Bq)

69
Q

How does the half life of an element change as the radioactivty decreases?

A

Half lives are constant

70
Q

How do you measure count rate to work out a substance’s half life?

A

Geiger counter

71
Q

What are sources of background radiation?

A

Rocks
The Sun
Food
Radon gas

72
Q

Why are rocks radioactive?

A

Rocks like granite contain small amounts of uranium salts

73
Q

How can we reduce our exposure to radioactive materials?

A

Shielding
Storage in lead/steel boxes
Rubber gloves, wash hands
No food or drink

74
Q

How does the age of a radioactive substance affect danger?

A

New radioactive substances are the most dangerous

75
Q

Why is iodine-123 suitable for treating cancer cells?

A

It has a short half life (13.2 hours)

Doesn’t damage many healthy cells

76
Q

Why is iodine-131 used in medical tracers for the thyroid gland?

A

Long enough half life (8 days) to monitor how well gland cuntions
Harm is limited as patient does not need extra doses

77
Q

How is radiation used in radiotherapy?

A

High doses of radiation can kill mutated cells (cancers) but also harms healthy cells

78
Q

What are cons of radiotherapy?

A

Can kill healthy cells- radiation sickness

Patients feel very unwell

79
Q

What are pros of radiotherapy?

A

High doses can kill mutated cells

Longer, healthier lives

80
Q

What is contamination?

A

When radioactive atoms or molecules get onto other materials

81
Q

What is irradiation?

A

When something is exposed to radiation on its outside

82
Q

What effects how harmful contamination is?

A

The type of radiation atoms emit

83
Q

How can we reduce irradiation?

A

Standing behind lead or storing radioactive materials in lead-lined boxes

84
Q

What are the 2 types of exposure to radiation?

A

Contamination

Irradiation

85
Q

Why is alpha radiation so dangerous to the body?

A

It cannot penetrate skin so stays inside the body

86
Q

What are tracers used to do?

A

Track blood flow around the body

87
Q

What type of radiation do tracers usually emit?

A

Gamma rays

88
Q

WHat does PET stand for?

A

Positron Emission Tomography

89
Q

Why do radioactive isotopes used in PET scanning have to be produced near the hospital?

A

They have a short half-life and will decay

90
Q

What is emitted in PET scanning?

A

Positrons

91
Q

What is the radius of an atom?

A

1 x 10^-10m

92
Q

What is the equation for the level or radiation due to a substance?

A

total level of radiation - level of background radiation = substance radiation

93
Q

What is the safest form of radiation outside of the body?

A

Alpha as it cannot enter the body

GCSE Physics (14 decks)

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