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Physics GCSE > Topic 6 - Radioactivity > Flashcards

Topic 6 - Radioactivity Flashcards

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1
Q

particle theory

A

a model that helps explain the properties of solids, liquids and gases

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2
Q

atomic model

A

models representing how an atom looks and behaves

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3
Q

atomic number

A

the number of protons

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4
Q

an atoms mass number

A

total number of protons and neutrons in the nucleus

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5
Q

isotope

A

atoms of the same element that have the same number of protons but DIFFERENT number of neutrons

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6
Q

explain the ‘plum pudding’ model

A
  • positive orb of energy with electrons inside
  • no nucleus
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7
Q

explain Rutherford’s model

A
  • dense positive nucleus with protons and neutrons
  • mostly empty space
  • electrons orbiting nucleus
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8
Q

where are protons

A

lives in the middle of the atom known as the nucleus and has a positive charge

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9
Q

where are neutrons

A

lives in the middle of the atom known as the nucleus and has no charge

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10
Q

electron

A

orbits around the nucleus and has a negative charge

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11
Q

what happens when an electron falls down an electron shell

A

it will release energy as light or EM radiation

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12
Q

ionising radiation

A

radiation that causes electrons to escape

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13
Q

emission spectrum

A

a series of colored lines that correspond to wavelengths emitted by the glowing gas

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14
Q

absorption spectrum

A

the parts of visible spectrum (visible light) that the gas absorbs when light passes through it

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15
Q

what are the sources of background radiation

A
  • food and drink
  • cosmic rays
  • ground and buildings
  • medical
  • radon gas
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16
Q

what’s the main source of background radiation

A

radon gas

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17
Q

background radiation

A

when we are constantly exposed to ionising radiation at a low level from space and from naturally radioactive substances in the environment

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18
Q

how does radon gas contribute to background radiation

A

this radioactive gas is produced by rocks that contains small amounts of uranium; radon diffuses into the air from rocks and can build up in houses, especially where there is poor ventilation

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19
Q

how does food and drink contribute to background radiation

A

some foods contribute to exposure background radiation because they contain small amounts of radioactive substances

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20
Q

how does medical contribute to background radiation

A

hospital treatment such as x-rays gamma scans and cancer treatment

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21
Q

how does cosmic rays contribute to background radiation

A

because they’re high energy charged particles that stream out the Sun and other stars

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22
Q

how can you measure radioactivity of a source

A

using a Geiger-Müller (GM) tube

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23
Q

how does a GM tube work

A
  • radiation calls through the tube ionising gas and inside it and allows a short pulse of current to flow
  • the GM tube can then be connected to counter to count the pulses of current, or the GM tube may give a click each time the radiation is detected - the account rate is a number of clicks per second or minute
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24
Q

what are the 3 types or radiation

A
  • alpha radiation
  • beta radiation
  • gamma radiation
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25
Q

why does decay or change happen in the nucleus of a radioactive substance

A

because the nucleus of a radioactive substance is unstable, which means it can easily change or decay

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26
Q

what happens when decay occurs

A

radiation is emitted, which causes a nucleus to lose energy and become more stable

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27
Q

what do alpha particles contain

A

2 protons, 2 neutrons

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28
Q

what is alpha particles relative mass

A

4

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29
Q

charge of alpha particles

A

2+

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30
Q

how is alpha particles written as

A

4
He
2

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31
Q

beta particles

A

high-energy, high-speed electrons

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32
Q

what’s beta particles relative mass

A

1/1835

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33
Q

beta particles charge

A

-1

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34
Q

what can beta particles be written as

A

0
e
-1

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35
Q

gamma rays

A

high frequency electromagnetic waves

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36
Q

electric charge of gamma rays

A

they don’t have a charge

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37
Q

what can all these radioactive waves do

A

they can penetrate (pass through) materials

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38
Q

what stops alpha particles penetrating

A

thin piece of paper - very ionising

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39
Q

what stops beta particles penetrating

A

thin sheet of aluminium - medium ionising

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40
Q

what stops gamma rays penetrating

A

block of lead - weakly ionising

41
Q

what happens to an atom when an alpha particle is emitted

A

the mass number goes down by 4 and the atomic number goes down by 2

42
Q

what happens in beta- decay

A

A neutron changes into a proton and an electron, atomic number increases by one, no change to the mass number
- electron is ejected from the atom

43
Q

what happens in a beta+ decay

A

a proton becomes a neutron and a positron, the mass number stays the same, the atomic number goes down by 1

44
Q

half life

A

the time taken for half the unstable nuclei in a sample of radioactive isotope to decay
- Measure of how long it takes for activity to half

45
Q

what happens in nuclear fission

A

large nuclei break up to form smeller nuclei and release energy

46
Q

nuclear fusion

A

two small nuclei collide and high speed to form a larger nuclei

47
Q

when does fusion happen

A

only happens at very high pressures/temperatures and the nuclei needs to be close together to fuse

48
Q

what is released in nuclear fission

A

high amount of energy and neutrons

49
Q

who came up with the ‘plum pudding’ idea

A

J.J Thompson

50
Q

how did Rutherford discover his idea

A

he fired alpha particles at gold foil
- some bounced back (reflected) because they were repelled by positively charged particles in the gold atom
- some alpha particles went straight through which indicated the atoms and mostly empty space

51
Q

how did Rutherford discover his idea

A

he fired alpha particles at gold foil
- some bounced back (reflected) because they were repelled by positively charged particles in the gold atom
- some alpha particles went straight through which indicated the atoms and mostly empty space

52
Q

Bohrs model of atom

A

Agreed with Rutherford, however he suggested that electrons can only be in a certain fixed orbit around the nucleus

53
Q

count rate

A

The number of clicks per second or minute

54
Q

positron

A

High energy high-speed particle

55
Q

positron relative mass

A

1/1835

56
Q

positron charge

A

+1

57
Q

how are positrons written

A

0
e
+1

58
Q

what can be emitted from an unstable nucleus

A
  • alpha particles
  • Beta particles
  • gamma rays
  • positrons
  • neutrons
59
Q

what can be emitted from an unstable nucleus

A
  • alpha particles
  • Beta particles
  • gamma rays
  • positrons
  • neutrons
60
Q

what happens when aplha particles are emited

A
  • transfer a lot of energy
  • each time they ionise an atom they loose energy
  • short penetration distance
  • very ionising
61
Q

activity of any radio active substance

A

Number of nuclear decades per second and is measured in becquerels (Bq)
- One becquerel is one nuclear decay second

62
Q

What are uses of radioactivity?

A
  • Food can be irritated with gamma rays to kill bacteria
  • surgical instruments need to be sterilised to kill microorganisms (heat them)
  • radioactive detecting (radioactive isotopes can be used as tracers)
  • Diagnose cancer using tracers in the body
  • Treat cancer
  • Checking thickness of paper
  • Smoke alarms
63
Q

Explain how radioactivity is used in radioactive detecting

A
  • When radiation passes inside a detector, it causes ionisation of gas atoms separating atoms into positive ions and electrons
  • separated electrons and positive irons are attracted to the electrodes causing a current to flow
  • This is converted into electrical signals which are then measured as the amount of radiation
64
Q

explain how radioactivity is used to check thickness of paper

A
  • when paper is too thin more bait particles penetrate the paper and the detector records a higher count rate
  • A computer senses that the account rate has risen and reduces the force supplied to the rollers to make the paper thicker
  • when the paper is too thick, the opposite happens
65
Q

explain how radioactivity works in smoke alarms

A
  • smoke alarms contain a source of alpha particles, usually a radioactive isotope called americium-241
  • The detector has an electrical circuit with an air gap between two electrically charged plates
    -The alpha particles ionise the air molecules and these ions then move across the gap forming a current
  • Smoking the device will slow down the ions and so make the current fall
  • The detective senses the amount of current if the current falls the siren sounds
66
Q

two dangers of radiation on the body

A
  • large amount of ionising radiation can cause tissue damage such as reddened skin
  • small amount of ionising radiation over a long period of time can cause damage of the DNA inside a cell (mutation)
    -> may cause cancer
67
Q

explain two precautions to handle radioactive sources

A
  • handle with tongs because the intensity of radiation decreases with distance from the source
  • Don’t point sources at people
  • Store in lead line containers as lead is an effective radiation shielding material because of its density
68
Q

when is someone irradiated and how it stops

A
  • someone is irradiated when they’re supposed to alpha beta or gamma radiation from nearby radioactive materials
  • Once a person moves away the irradiation stops
69
Q

When does someone become contaminated and how will it stop?

A
  • someone becomes contaminated if they get particles of radioactive material on their skin or inside their body
  • This will continue until the material has all decayed until the source of contamination is removed (which is not always possible)
70
Q

Explain some medical ways to use gamma ray tracers - gamma cameras

A
  • They can be injected into the bloodstream, swallowed, inhaled or injected directly into an organ
  • Can be found to find sources of internal bleeding
  • gamma cameras are used to detect tumours
71
Q

how do gamma cameras find internal bleeding

A

gamma cameras detect the area of highest gamma radiation which is where the bleeding is occurring

72
Q

how do gamma cameras detect tumours?

A

Tracer is made using radioactive glucose molecules because very active cells such as cancer cells take up glucose more quickly than other cells

73
Q

gamma camera

A
  • gamma cameras image the radiation from a tracer introduced into the patient’s body
    -> the text grammar is emitted by radioactive isotopes in the body
74
Q

radioactive tracers

A

they contain an radioactive isotope attached to molecule that will be taken up by a particular organ in the body to track the movement of a substance or it’s location

75
Q

what do radioactive isotopes used in medical tracers need to have a short half life?

A

other parts of the body are affected as little as possible

76
Q

what is used in internal radiotherapy

A

uses a beta emitter placed close to a tumour

77
Q

what is used in external radiotherapy

A

Uses beams of gamma rays x-rays or protons directed at the tumour from outside the body

78
Q

nuclear fission

A

a large nuclei (uranium-235) breaks up to form smaller nuclei and release energy

79
Q

name a nucleus fuel

A

uranium-235

80
Q

+ and - of nuclear power station

A
  • produce waste that will stay radioactive for millions of years
  • very expensive to decommission
    + low greenhouse gas emissions
81
Q

benefits of nuclear fuel

A
  • store a lot more energy per kg
  • do not burn so don’t need air to allow them to release energy
82
Q

fossil fuel power station + and -

A
  • burning fossil fuel produce CO2 - contribute to climate change
    + cost efficient
83
Q

explain what happens in nuclear fission and what is release

A

when a uranium-235 absorbs a neutron, it immediately splits into two smaller daughter nuclei; two more neutrons are released - neutron store a lot of kinetic energy cause they’re moving at high speeds

84
Q

Uncontrolled nuclear fission chain reaction

A

When the neutrons released or absorbed by another uranium-235 nuclei - these nuclei will become more unstable and release more neutrons when they’re nuclear splits; these neutrons can be absorbed by more uranium nuclei and so on

85
Q

how to stop a chain nuclear fission reaction

A

Other materials absorb some of the neutrons

86
Q

function of control rods in a nuclear reactor

A

to control the rate of fission by absorbing neutrons (control the chain reaction)

87
Q

where are control rods in a nuclear reactor

A

placed between the fuels in the reactor core

88
Q

explain the function of fuel rods in a nuclear reactor

A

they power nuclear reactors
- in a nuclear reactor the fuel is made as into fuel rods and as fission reactions occur, neutrons leave fuel rods at high speed

89
Q

what increases the chances of a neutron being absorbed by a uranium-235 nucleus

A

If the neutrons are moving slowly

90
Q

what increases the chances of a neutron being absorbed by a uranium-235 nucleus

A

If the neutrons are moving slow slowly

91
Q

where are fuel rods inserted

A
  • inside a reactor core - into holes in a material called a moderator
92
Q

function of moderator in a nuclear reactor

A

to slow down neutrons produced by fission that the chain reaction can be sustained which makes it more likely for fission to occur

93
Q

how to generate electricity from a nuclear reactor

A
  • Energy released from the reactor core is transferred into a coolant
  • The hot coolant is pumped to a heat exchanger which is used to make steam
  • The steam drives a turbine which turns a generator to produce electricity
94
Q

what is the lost mass from nuclear fusion converted into

A

energy
- The mass of the new nucleus formed is slightly less than the total of the masses of the two smaller nuclei

95
Q

electrostatic repulsion

A

the protons in the nuclei are positively charged so like charges repel

96
Q

when can electrostatic repulsion be overcome so that nuclei can fuse

A

If the nuclei is close enough or is travelling fast enough

97
Q

+ and - of building a commercial fusion power station (fusion nuclear reactor)

A
  • difficult to sustain the extreme temperatures and pressures required for fusion
  • The recipe produce a lot more energy than fission reactors
    + a few problems with safely disposing of radioactive waste materials from fusion reactors
98
Q

What is a property that an isotope must have to be suitable to use in an RTG?

A

Have a long half life as the Rover needs to operate for a long time on Mars

Physics GCSE (9 decks)

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