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GCSE Physics > 7. Radioactivity & particles > Flashcards

7. Radioactivity & particles Flashcards

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1
Q

definition of atom

A

positively charged nucleus containing protons + neutrons

smaller negative electrons orbiting outside the nuclus in shells

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2
Q

definition of mass number

A

protons + neutrons

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3
Q

definition of atomic number

A

no. of protons

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4
Q

how to work out no. of neutrons

A

mass no. - atomic no.

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5
Q

definition of isotope

A

same no. of protons but different no. of neutrons

same atomic no. different mass number

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6
Q

in terms of symbol notation which no. is the mass no. and which one is the atomic no.

A

mass no. = top no

atomic no. = bottom no.

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7
Q

definition of ion

A

atom which has gained or lost 1 or more electrons

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8
Q

loss of electrons = ? charge

A

positive charge

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9
Q

gain of electrons = ? charge

A

negative charge

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10
Q

what are alpha particles, beta particles and gamma rays

A

ionising radiations emitted from unstable nuclei in a random process

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11
Q

what causes ionisation

A

nuclear radiation

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12
Q

how does nuclear radiation cause ionisation

A

by bashing into atoms and knocking electrons off them

( the further the radiation can penetrate before hitting an atom the less damage it will do along the way = less ionising)

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13
Q

what can be used to detect ionising radiation

A

Geiger-Muller detector

photographic film

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14
Q

what is an alpha particle and its properties

A

helium nuclei = 2 protons and 2 neutrons

big, heavy + slow moving

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15
Q

what is the penetrating power alpha particles

A

slow moving and heavy = don’t penetrate far into materials but are stopped quickly

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16
Q

what can alpha particles be blocked by

A

paper
skin
few cm of air

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17
Q

what is an alpha particles ability to ionise like

A

(alpha particles are) big= strongly ionising=

bash into a lot of atoms + knock electrons off them before they slow down = creation of lots of ions

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18
Q

what kind of electrical charge do alpha particles have

A

positive

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19
Q

what does alpha particles being positively charged result in

A

alpha particles being deflected by electric + magnetic fields

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20
Q

what does emitting an alpha particle do to the atomic no. and mass no.

A

atomic no. = -2

mass no. = -4

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21
Q

what is a beta particle and its properties

A

electron

electron which has been emitted from the nucleus of an atom when a neutron turns into a proton and an electron

move quite fast + quite small

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22
Q

what is the penetrating power beta particles

A

quite fast = penetrate moderately before colliding

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23
Q

what can beta particles be blocked by

A

thin metal

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24
Q

what is an beta particles ability to ionise like

A

quite small = moderately ionising

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25
Q

what kind of electrical charge do beta particles have

A

negative

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26
Q

what does beta particles being negatively charged result in

A

deflected by electric and magnetic fields

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27
Q

what does emitting a beta particle do to the atomic no. and mass no.

A

atomic no. = +1

mass no. = stays the same

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28
Q

what is a gamma ray and its properties

A

energy (in the form of an EM wave )
have no mass
( opposite of alpha particles )

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29
Q

what is the penetrating power of gamma rays

A

penetrate a long way into materials without being stopped

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30
Q

what can gamma rays be blocked by

A

thick lead

thick concreate

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31
Q

what is gamma rays ability to ionise like

A

weakly ionising because pass through rather than collide with atoms ( but eventually hit something and do damage)

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32
Q

what kind of charge do gamma rays have

A

no charge

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33
Q

what does gamma rays having no charge result in

A

not deflected by electric or magnetic fields

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34
Q

when does gamma emission occur

A

always happens after beta or alpha decay
you never get just gamma rays emitted

when a nucleus has excess energy= looses energy by emitting gamma ray

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35
Q

what does emitting a gamma ray do to the atomic no. and mass no.

A

no effect
atomic no. = stays the same
mass no. = stays the same

36
Q

need to be able to balance nuclear equations in terms of mass and charge

A

???

37
Q

name 2 sources of background radiation

A

Earth
space
(living things and human activity)

38
Q

explain the sources of background radiation from earth

A 
radioactivity comes from:
air
food
building materials 
soil
rocks
39
Q

explain the sources of background radiation from space

A

radiation from space ( cosmic rays) - mostly from the sun

40
Q

what happens to the activity of a radioactive source over a period of time

A

it decreases

41
Q

what is the activity of a radioactive source measured in

definition of activity

A

becquerels ( Bq) ( 1 Bq = 1 decay per second)

no. of decays in a given time

42
Q

definition of half life

A

time taken for half of radioactive atoms now present to decay

(time it takes for a radioactive material to lose half of its radioactivity)

( time taken for the activity (or count rate) to fall by half

43
Q

the older something is what happens to the radioactivity

A

decreases= less radiation is emitted

44
Q

what is the rule about half life

A

it is varied = different for different radioactive isotopes = some take just a few hours and some millions of years

45
Q

know how to calculate half life in equations and graphs

A

???
eg 4 half lives of 640=40
640 divided by 2 4 times
easier way = 640 divide by2 to the power of 4

46
Q

uses of radioactivity in medicine

A

medical tracers

treat cancers- radiotherapy

47
Q

what kind of radiation do medical tracers use and why

A

beta and gamma
they penetrate the skin and other body tissues

(alpha = bad= stopped by body tissues= never detect it externally + strong ionising power= harmful if inside you )

48
Q

how do medical tracers work

A
  1. source which emits beta or gamma radiation is injected ( or swallowed) into patients
  2. radiation penetrates the body tissues and can be detected externally
  3. source moves around body- radiographer uses a detector and computer to monitor its progress
  4. doctors use this method to check whether organs of the body are working properly
  5. radioactive source = short half life= initial levels are high enough to be easily detected, but radioactivity in patient quickly disappears
49
Q

what kind of radiation does radiotherapy use

A

gamma rays

50
Q

how does radiotherapy work

A
  1. kills cancer cells + stops them dividing
  2. uses a high doses of gamma rays carefully directed to zap the cells in the tumour
  3. while minimising the dose to rest of the body
51
Q

uses of radioactivity in industry

A

sterilisation of food and equipment
tracers
thickness gauges

52
Q

what kind of radiation is used to sterilise food an equipment

A

gamma rays

53
Q

how does sterilisation work

A

food and equipment can be irradiated with a high dose of gamma rays to kill all microbes = doesn’t go bad as quickly as it would otherwise

54
Q

why is irradiation a good method of sterilisation

A

unlike boiling, it doesn’t involve high temp= fresh fruit or plastic instruments = totally sterilised without being damaged

55
Q

what kind of radiation is used in industry tracers

A

gamma - can pass through any rocks or earth surrounding pipes

56
Q

how do gamma emitting tracers work

A
  1. detect leaks in underground pipes
  2. source flows down pipe and detector used above ground
  3. crack in the pipe= more radiation collects outside pipe = detector show extra high radioactivity at that point
  4. source = short half life= don’t cause long term hazard if it collects somewhere
57
Q

what kind of radiation does thickness gauges (thickness control) use

A

beta radiation is used in thickness control

paper will partly block the radiation ( if it all goes through or none of it does= reading wont change at all as thickness changes)

58
Q

how does thickness control work

A
  1. direct radiation through stuff being made (eg paper)
  2. put detector on other side, connected to control unit
  3. detected radiation level changes= paper is coming out to thick or thin
  4. control unit adjusts rollers to give right thickness
59
Q

definition of irradiation

A

exposure to radiation

60
Q

how do you reduce the risk of the irradiation

A

keeping sources in lead-lined boxes
standing behind barriers
being in different room and using remote-controlled arms

61
Q

definition of contamination

A

unwanted radioactive atoms get onto or into an object

contaminating atoms might decay =release radiation=harmful

62
Q

why is contamination especially dangerous

A

radioactive particles could get inside your body

63
Q

how do you reduce the risk of contamination

A

gloves and tongs - stop particles getting stuck to skin or under nails

protective suits and mask- stop breathing in particles

64
Q

what are dangers of ionising radiation

A
  1. cause mutations in living organisms= cells divide uncontrollably = cancer
  2. damage cells and tissues
65
Q

effects of radiation ( bad ones )

A

low dose= mutated cell = cancer

high dose = dead cell= radiation sickness

66
Q

what is difficult about the disposals of (high-level) radioactive waste

A

its is difficult to dispose safely – stays highly radioactive for tens of thousands of years

67
Q

how is low level radioactive waste disposed ( from nuclear power stations and hospitals eg. clothing +syringes)

A

burying it in secure landfill sites

68
Q

how is high level radioactive waste disposed

A

sealed into glass blocks,
then sealed in metal canisters
,then buried deep underground

69
Q

what is the problem with the disposal of high level waste

A

difficult to find suitable paces to bury it

site needs to be geologically stable ( not suffer from earthquakes) - movement of rock disturb canister = radioactive material to leak out

if material gets into ground water = contaminate soil, plants, rivers + drinking water

70
Q

name 3 types of nuclear reaction

A

fission
fusion
radioactive decay

71
Q

what are nuclear reactions source of

A

source of energy

72
Q

definition of nuclear fission

A

splitting of an atom, which releases energy

73
Q

where is nuclear fission purposely made to happen

A

nuclear reactor eg. happens to uranium-235

energy = transferred to thermal energy stores =produce steam =drive turbine

74
Q

what happens to uranium-235 in a nuclear reactor

A

nucleus can be split ( by fission) by collision with a neutron, = releases energy as kinetic energy of the fission products

75
Q

what does the fission of Uranium-235 produce

A

2 radioactive daughter nuclei + a small no. of neutrons

76
Q

definition of a chain reaction in terms of fission

A

slowing moving neutron absorbed by uranium-235= nucleus splits

release small no. of neutrons = go on to hit other uranium-235 nuclei= causing split and so on……

77
Q

describe the neutrons released in a nuclear reactor and their problem

A
  1. neutrons released by fission reactions in nuclear reactor have a lot of energy
  2. in order for neutrons to be absorbed by uranium nuclei and sustain a chain reaction they need to be slowed down
78
Q

what 2 methods are used to control the released neutrons

A

moderator

control rods

79
Q

definition of moderator ( in a nuclear reactor)

A

usually graphite or water = slows down neutrons

80
Q

definition of control rods ( in a nuclear reactor)

A

often made from boron = limits the rate of fission by absorbing excess neutrons

81
Q

what is the role of shielding around a nuclear reactor

A

used to absorb ionising radiation ( which is released from high energy neutrons and gamma rays which are released during fission )

shielding= thick concreate structure which may contain lead or other metals

82
Q

definition nuclear fusion

A

creation of larger nuclei resulting in a loss of mass from smaller nuclei, accompanied by a release of energy

opposite of fission = joining small nuclei

2 light nuclei collide at high speed and join (fuse) to create a larger, heavier nucleus.

eg. hydrogen nuclei can fuse to produce a helium nucleus

83
Q

what is fusion the energy source for

A

stars

all energy released in stars comes from fusion

84
Q

why does fusion only happen at really high temps and pressures

A

positively charged nuclei have to get very close to fuse, so need to be moving very fast to overcome the strong force due electrostatic repulsion of protons

85
Q

explain differences between nuclear fission and fusion

A 
fission = splitting of nucleus 
fusion= joining of nuclei

fusion = releases a lot more energy than fission for a given mass of fuel

GCSE Physics (8 decks)

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