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edexcel igcse physics > unit seven: radioactivity and emissions > Flashcards

unit seven: radioactivity and emissions Flashcards

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1
Q

symbol for alpha radiation

A

a

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2
Q

symbol for beta radiation

A

β- or β+

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3
Q

symbol for gamma radiation

A

g

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4
Q

symbol for neutron radiation

A

n

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5
Q

what is alpha radiation made from

A

a helium nucleus: 2 protons and 2 neutrons

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6
Q

what is beta radiation from

A

a high speed electron or beta particle

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7
Q

what is gamma radiation made from

A

a high energy wave

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8
Q

properties of the gamma wave radiation

A

high frequency

short wavelength

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9
Q

what does alpha radiation do to the atomic number of the parent atom

A

decrease by 2 (2 protons and 2 neutrons)

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10
Q

what does beta radiation do to the atomic number of the parent atom

A

decrease by 1 (1 electron)

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11
Q

what does gamma radiation do to the atomic number of the parent atom

A

nothing

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12
Q

what does neutron radiation do to the atomic number of the parent atom

A

nothing

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13
Q

what is neutron radiation made from

A

an emitted neutron

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14
Q

what does alpha radiation do to the mass number of the parent atom

A

decrease by 4 (2 protons and 2 neutrons)

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15
Q

what does beta radiation do to the mass number of the parent atom

A

nothing

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16
Q

what does gamma radiation do to the mass number of the parent atom

A

nothing

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17
Q

what does neutron radiation do to the mass number of the parent atom

A

decrease by 1 (1 neutron)

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18
Q

what happens when you fire an alpha particle

A

the atoms interact with other atoms along their path causing ions to form

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19
Q

what happens when you fire a beta particle

A

the atoms interact with other atoms along their path causing ions to form, but less frequently then alpha as beta particles are smaller than alpha particles and carry less charge

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20
Q

what charge does a beta particle have

A

-1

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21
Q

order alpha beta gamma in order of ionising power

A

alpha (strongest)
beta
gamma (weakest)

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22
Q

what is alpha stopped by

A

paper

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23
Q

what is beta stopped by

A

thin aluminium

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24
Q

what is gamma stopped by

A

thick lead sheet

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25
Q

what is the only type of radiation that can cause other atoms to become radioactive

A

neutron

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26
Q

what happens during alpha decay

A

loss of 2 protons and 2 neutrons
= mass number decreases by 4
= atomic number decreases by 2

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27
Q

what happens during beta decay

A

neutron breaks down to give a proton and an (emitted) electron
= mass number stays the same
= atomic number increases by 1

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28
Q

what happens during gamma decay

A

a gamma ray is emitted (not charged)

gamma ray energy is 1 x 10 to the minus 12 joules.

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29
Q

what happens during neutron decay

A

high speed neutron emitted
= atomic number stays the same
= mass number decreases by 1

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30
Q

what is half-life

A

the time taken for half the original number of unstable nuclei to decay. The half-life of a particular radioactive isotope does not change.

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31
Q

what is rate of decay measured in

A

becquerels, Bq

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32
Q

what is one Bequerel

A

one decay per second

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33
Q

explain natural background radiation from earth

A

when earth was formed it produced many radioactive isotopes. uranium was produced, and it also decays very slowly producing gases as it does so. these gases come out of rocks, and this means radiation from the big bang is still present, being released through rocks in the earth.

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34
Q

explain natural background radiation from space

A

supernovae produce cosmic rays that coninuously hit the earth. lower energy cosmic rays are given out by the sun. the earth can only protect us from some of these rays

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35
Q

explain radiation in living things

A

the atoms in our bodies were made from violent reactions. as some of these atoms are raditoactive, and we constantly breathe in tiny amounts of radioactive carbon-14, and it behaves chemically just like the stable isotope carbon-12, we continuously renew the amounts of carbon in our bodies.

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36
Q

explain artificial radiation (examples)

A

nuclear power stations
nuclear weapons
radioactive tracers

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37
Q

how is radiation used in medicine

A

radioactive tracers
iodine-123 can be absorbed by thyroid gland allowing clear images to be taken
techtium-99 medical imaging
can be used to kill cancerous cells

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38
Q

industrial applications of radioactivity

A

gamma rays used to examine contents of luggage
to gauge how much material there is in a storage container
to gauge thickness of sheets
to check flow of liquids
carbon-dating

39
Q

what is contamination

A

Contamination - radioactive material has been transferred into a different substance, it will remain radioactive until the radioactive substance has decayed to a safe level.

40
Q

what is irradation

A

a material has been dosed with radiation to kill germs etc, when the radiation is stopped, there is no radioactivity in the sample.

41
Q

dangers of ionising to living things

A

damages dna within cells

exposed material will give out light when warmed

42
Q

how is radioactive waste handled/safety precautions

A

kept in lead lined containers
large samples handled remotely
sealed in containers capable of handling it for massive amounts of time

43
Q

which element is the fuel rods of reactors

A

uranium

44
Q

which isotope is used for nuclear fission

A

uranium-235

45
Q

how many uranium pellets are in a whole reactor

A

over 2 000 000

46
Q

what substance is used to slow down neutrons in a nuclear reactor

A

water

47
Q

what happens when the neutron hits the nucleus of the uranium atom

A

It causes the nucleus to split in two. (the fission) and releases its own neutrons, hitting other nuclei and causing more fisson.

48
Q

what particles are released when fission happens

A

neutrons

49
Q

what is a chain reaction in the context of nuclear fission

A

neutrons emitted from the initial collision hit other nuclei causing more neutrons to be emitted

50
Q

how many fissions happen a second in the reactor

A

5 million million

51
Q

what does the hot water from the reactor do after it leaves the reactor

A

The water hits more than 300 degrees celsius and the heated high pressure water travels out through pipes out of the reactor vessel at 35 mph through

52
Q

what is the output of the power station

A

1000 MV

53
Q

what isotopes of hydrogen collide at high speed during fusion

A

deutrieum and tritium

54
Q

what forms as a result of the collision between deutrieum and tritium

A

a helium nucleus
a neutron
large amount of energy

55
Q

what is the fusion process an energy source of

A

the sun and all stars

56
Q

advantages of fusion

A

does not produce radioactive waste

uses materials more readily available than the uranium found in conventionalfission reactors

57
Q

problem with fission

A

very very high temperatures (100 milion celsius) are needed to make the deuterium and tritium collide with enough energy to overcome the repulsive force between the positive electric charge in the nuclei of each atom

58
Q

what must the very high temperatures needed for fusion be stored in

A

a very strong magnetic field or magnetic bottle. the pressure must be very high.

59
Q

how much smaller is the electron compared to the diameter of the atom

A

the diameter of the nucleus is about 10,000 times smaller than the diameter of the atom

60
Q

what symbol is given to atomic number

A

Z

61
Q

what symbol is given to atomic mass

A

A

62
Q

what determines atomic mass

A

total number of protons and neutrons

63
Q

what determines atomic number

A

number of electrons

64
Q

what is an isotope

A

an atom with the same number of protons and different numbers of neutrons

65
Q

physical differences in isotopes

A

mass

stability of nucleus

66
Q

why does stability of isotopes vary

A

protons are held in place by nuclear force, which stops the protons repelling away from eachother. the neutrons affect the balance, and cause unstability

67
Q

describe the range of alpha radiation

A

short ionising radiaiton range.

68
Q

which is lighter beta or alpha

A

definitely beta

69
Q

why does beta have a higher range than alpha

A

beta particles are smaller and carry less charge so interact with other particlesl ess, so they have a greater range, and can travel long distances.

70
Q

why do alpha particels have a short range

A

they interact with atoms along their paths causing ions to form. this means they rapidly give up energythat they had when they were ejected from the unstable nucleus.

71
Q

describe gamma rays

A

very short wavelengths. no mass and no charge. weakly ionising

72
Q

do gamma rays have a large range

A

yes they are extremely penetrating (as they are weakly ionising and only interact with a few atoms in their path) and can pass through all but the very densest materials.

73
Q

how must radioactive sources be stored

A

in lead-lined boxes in a metal cupoboard with radiation warning label

74
Q

how did henri bequel test if uranium emitted -rays after being exposed to sunlight and what were the results

A

placed some wrapped, unused photographic plates in a drawer with some samples of uranium ore on top of them. he fpund a stron image of th eore on the plates when he developed them. he had discovered radioactivity

75
Q

what does the unit the Becquerel measure

A

the measure of how many unstable nuclei are disintegrating per second

76
Q

what does one becquerel mean

A

a rate of one disintegration per second.

77
Q

what is a kBq

A

a rate of 1000 disintegrations per second

78
Q

what is a MBq

A

a rate of 1 000 000 disintegrations per second

79
Q

what is a Geiger-Muller tube

A

a glass tube with an electrically conducting surface on the inside. the tube has a thin window made of mica, and the tube contains a special mixture of gasesat a very low pressure. inside, there is an electrode. this electrode is connected via a high value resistor to a high voltage supply, typically 300-500 V.`

80
Q

what is mica

A

a naturally ocuring mineal that can be spit into thin sheets

81
Q

how does a GM tube work

A

when ionising radiation enters the tube it causes the low pressure gas inside to form ions. these allow a small amount of current to flow from the electrode to the conducting layer. it is usuallly linked up to a counting circuit. this keeps a count of how many ionising particles or how much y radiation have entered the GM tube.

82
Q

sources of natural background radiation from the earth

A

rocks in the earths’ crusts (some of which are still producing radiation) which can be released through radioactive rocks (if gases),

83
Q

forms of uranium that are decaying very slowly

A

radon and thoron

84
Q

how is the natural background radiation from space

A

violent nuclear reactions in stars and exploding stars called supernovae produce cosmic rays (very energetic particles) that continuously hit the earth. lower energy cosmic rays are given out by the sun.

85
Q

radiation in living things

A

the atoms that make up our bodies were formed in the violent reactions that take place in supernovae billions of years ago. we also breathe in tiny amounts of carbon-14

86
Q

artifical radiation

A

generating electricity in nuclear power stations leaks radioactive material into the environment.
testing nuclear weapons
radioactive tracers are used in industry and medicine

87
Q

is radioactive decay random

A

yes you cannot predict it with certainty

88
Q

what is halflife def

A

the average time taken for half the original mass of the sample to decay. if the amount of radioactive matter has halved then the activity of the decay haves.

89
Q

does the half life vary

A

yes it is different for every isotope

90
Q

how do you measure half life

A

use a GM tube linked to a rate meter. subtract background radiation. then measure the rate of decay of the sample at regular time intervals. the rate of decay is shown by the count rate on the rate meter.

91
Q

how to record measuring half life

A

overall title: average background radiation measured over x minutes

then columns of:
time, t/min count rate/Bq corrected count rate C/Bq

92
Q

the rate of decay is proportional to…

A

the amount of radioactive isotope present

93
Q

which isotopes are suited to medical use and why

A

isotopes with short half lives because the activity of a source will become very small as the isotope decays quickly.

edexcel igcse physics (13 decks)

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