Radioactivity Flashcards
1
Q
What is a nuclear symbol
A
The whole square information of the element
2
Q
What is an isotope
A
Atoms of the same element that have same number of protons but different number of neutrons
3
Q
Give two properties of isotopes
A
-have different physical properties to each other
-have different stabilities of the nucleus
4
Q
What causes an isotope to be unstable
A
If there are too few or too many neutrons or protons,
which can disrupt the nuclear force holding the nucleus together
5
Q
Explain how atoms become stable
A
They emi radiation to become more stable,
Which can be in the form alpha beta or gamma
And this causes energy to be lost from the nucleus, making it more stable
6
Q
Give two properties of radioactive decay
A
-a random process
-unable to predict when it will happen
7
Q
What is ionisation
A
The addition or removal of an electron to create an ion
8
Q
Explain how ionisation occurs
A
The outer electrons absorb energy in the form of ionizing radiation (alpha, beta, gamma), causing them to leave the atom
This means that the atom contains more protons than electrons, so it will become a positively charged proton
9
Q
What is ionizing radiation
A
-The type of radiation that can ionize atoms that it hits (so cause it to go from atom to ion)
-The examples are alpha beta and gamma
10
Q
What is an alpha particle
A
A helium nucleus, because it contains two neutrons and two protons
11
Q
Why is a beta particle and how is it formed
A
A fast moving electron,
which is emitted from a nuclei
when a neutron decays into a proton and electron
12
Q
What is a gamma ray
A
An electromagnetic wave with the most amount of energy out of all the electromagnetic waves
13
Q
Charge of alpha particle
A
2+
14
Q
Charge of beta particle
A
1-
15
Q
Charge of gamma ray
A
0
16
Q
RAM of alpha particle
A
4
(2 protons and 2 neutrons)
17
Q
RAM of beta particle
A
Virtually none or 1/1800
18
Q
RAM of gamma ray
A
None, because it’s a wave so has no mass
19
Q
Order the penetrating powers of the 3 types of radiation,
From most penetrating to least penetrating, and explain why
A
Gamma (a wave so can travel quite far)
Beta (moderately penetrating)
Alpha (least penetrating because largest size)
20
Q
Explain why …. Are the least penetrating but the most ionizing forms of radiation
A
Alpha particles
Least penetrating because of their large mass and size
Most ionizing because of their 2+ charge, so can easily knock electrons off
21
Q
State how far each form of radiation can travel in air, in order of the most penetrating to least penetrating
A
Gamma rays: infinite distance in air
Beta particles: few 10s cm in air
Alpha particles: few cm in air
22
Q
Alpha particles are stopped by….
A
Sheet of paper
23
Q
Beta particles can travel through…. But are stopped by…
A
Sheet of paper
Few mm of aluminum
24
Q
Gamma rays can travel through… but are partially stopped by
A
Sheet of paper + few mm of aluminum
Few mm of lead
25
State which material each type of radiation is stopped by
Alpha: sheet of paper
Beta; few mm of aluminum
Gamma: few mm of lead (but only partially stopped by it)
26
When a substance undergoes radioactive decay, state the four types of radiation that can be emitted
Alpha
Beta
Gamma
Neutron
27
State how a neutron can be emitted through radio active decay
If the nuclei of the atoms contains too many neutrons, then they will be released to make the atom more stable
28
State two ways to detect radiation
Using a Geiger- Müller tube
Using photographic film
29
Describe how a Geiger muller tube works
It absorbs radiation
which is the transmitted as an electrical impulse
To either a counter which displays the count rate
Or as a clicking sound
30
What is the count rate, when using a Geiger muller tube
The number of decays detected per second
31
Describe how photographic film can be used to detect radiation
It consists of different materials like aluminum and lead and becomes darker when it absorbs some radioactive material
32
Explain which types of radiation are likely to be detected on a photographic film badge
Alpha radiation is unlikely to be detected as it will be absorbed/stopped by the paper
Beta radiation is likely to be absorbed by the aluminum
Gamma radiation is likely to be detected throughout the badge, however some of the radiation may be absorbed by the lead
33
The radiation received by a person is measured in…., and can lead to..
SIEVERTS (sv)
Acute radiation poisoning
34
Describe the experiment on how you can investigate the penetrating powers of radiation
1)Connect the Geiger muller tube to a counter and measure the background radiation, without any sources nearby
2)repeat 3 times and then take an average
3) take out a radioactive source using tongs, and place a fixed distance near to the tube
4)take an absorber, and place it in between the tube and the source, and then take a reading after a one minute interval
5)repeat with different absorbers
6)then repeat the whole experiment again with a different source
35
Give two safety precautions when investigating the penetrating powers of radioactive sources
1)always keep the source a distance away from you
2)use a lead lined container to store the materials at all time
36
Give three ways that you can ensure minimum errors in the experiment to investigate penetrating powers
1)use a material with a long half life and activity
2)when measuring background radiation, make sure sources are a good distance away to avoid disruptions
3)make sure all repeats of the experiment are done in the same location so that they have the same background radiation
37
What is background radiation
The radiation that exists all around us all the time
38
State 4 types of natural sources that emit background radiation
-radon gas from uranium that decays
-cosmic rays from space
-carbon-14 in all organic matter
-in good and drink, eg potassium-40 in bananas
39
Explain how radon gas is a source of background radiation, and how it’s dangerous
Uranium, a naturally radioactive material found in rocks
Can decay into radon gas
Which emits alpha particles
Which if inhaled into lungs can be dangerous
40
Explain how cosmic waves from space become a source of background radiation
The sun emits protons
Which enters the earth at high speeds,
Then these protons collide with molecules in the air which produces gamma rays
41
State three examples of man made background radiation
Medical sources such as X-rays, CT scans and radioactive tracers
Nuclear fallout from nuclear weapons
Nuclear accidents
42
Give four uses of radioactivity
-alpha particles in smoke detectors
-beta particles in thickness gauges
-gamma rays in radio therapy and tracers
-sterilizing food and equipment
43
Explain how alpha particles are used in smoke detectors
1)a radioactive source emits alpha radiation, which ionizes the air around them causing a current to flow in the circuit gap
2)when smoke enters, they absorb the alpha particles (which have a weak penetration power)
3)so the current will stop
4)the alarm can no longer detect a current and this triggers the alarm
44
Explain how beta particles are used in thickness gauges
1)the material passes through between a detector and beta emitter
2) when the material is too thick, more beta particles are absorbed and less penetrate through and are detected
3) and then when the material is thinner, less beta particles are absorbed and more penetrate through and are detected
4)the machine is thus able to make adjustments inorder to keep the thickness at a constant rate
45
Explain why beta particles are used in thickness gauges and not alpha or gamma
Beta particles are partially penetrating,
But if alpha were used which are weak penetrators, they would all be absorbe3d by the material and none would be detected
And if gamma particles used, which are strong penetrators, then almost all would penetrate through and be detected, so the machine would not be able to detect changes in thickness
46
Explain why alpha particles are used in smoke detectors and not beta or gamma
Alpha particles are strongly ionizing and so can create a current
Beta and gamma would not be able to with their ionizing ability
Alpha particles are also weakly penetrating so are able to be absorbed by the smoke and stop the current
Beta which is partially penetrating and gamma which is highly penetrating would simply pass through the smoke and would not be able to stop the current
47
Explain how radiotherapy works
Beams of gamma rays are directed at the cancerous tumor
The gamma rays are highly penetrating so are able to penetrate through the body
48
Explain how a radioactive tracer works
A Radioactive tracer is a radioactive isotope which is injected or swallowed into the body
This emits beta or gamma radiation which penetrates through the body and can be detected externally
So doctors can monitor whether or not particular organs are working properly
49
Which type of particles are used for radioactive tracers and explain why
Beta or gamma particles because they are penetrating and not ionizing swo can not damage cells
Alpha particles are weakly penetrating and strongly ionizing so would be able to kill healthy cell
50
Give a property that the radioactive isotope in a medical tracer must have and explain why
A short half life
So that initially levels can emit large amounts of radiation to be detected
But so that it will quickly disappear from the patient
51
Give two properties that gamma rays used to sterilize medical equipment must have and why
Must have a long half life so that they dont need to be replaced very often
Must be a strong source of gamma so that it is strongly penetrating
52
Why is sterilizing food better than boiling it to kill microbes
Because no high temperatures are used so the food can remain undamaged
53
Give two definitions of half life
The amount of time required for the sample of radioactive nuclei to halve
Or
The amount of time required for the activity(the number of decays) to halve
54
What is activity
The overall rate of decay of all the isotopes in the sample
55
What is activity measured in
Bequerels
56
3 Bequerels is the same as saying
3 radioactive nuclei decay per second
(Because remember that Bequerels is activity, which is the rate of decay)
57
Carbon 14 has a half life of 5700 years, explain what this means
Give two interpretations
It means that it takes 5700 years for the sample to become 50 percent of its origina value
Or
It takes 5700 years for the activity, or the number of decays per second to become half of what it originally was
58
Explain why activity decreases over time
Because as time increases, the number of radioactive (unstable)nuclei in the sample decreases
So there are less nuclei left to decay
So therefore the overall activity decreases
59
Why is contamination more harmful than irradiation
Because of the continuous exposure to radiation
Because in irradiation, once the source is removed the object will no longer be exposed to radiation
But once a radioactive isotope goes onto an object, it will keep emitting radiation
60
Explain what it means if a substance has a short half life
And what it means if it has a long half life
Short half life means that it has a higher activity,
So has a higher rate of radioactive emissions
Long half life means that it will stay active for longer
So more care is required to control it for longer, with mechanisms such as shielding or storage
61
Definition of contamination
The unwanted presence of materials containing radioactive isotopes on other material,
Where this causes the other material to begin to emit radiation and become radioactive itself
62
Definition of irradiation
The process of exposing a material to alpha, beta, or gamma radiation,
Where the material itself exposed however will not become radioactive
63
Explain how contamination can occur
When a radioactive isotope gets onto another material where it should not be
This causes the material itself to begin to emit radiation and become radioactive itself
64
Why does irradiation not make objects become radioactive
Because an object will only become radioactive if it contains radioactive isotopes
But in irradiation the object will only be exposed to the radiation coming from the radioactive isotope itself
65
Give two difference between irradiation and contamination
In contamination, the object will contain the radioactive isotope,
But in irradiation, the object will only be exposed to the radiation emitted by the radioactive isotope
In contamination, the object will remain radioactive as long as the source is on it or in it, and even when it is removed, it is difficult to remove the radiation,
But in irradiation, the effect of the radiation emitted by the source will stop as soon as the radiation is removed
66
Explain a method of protection when dealing with contamination,
And describe which type of people deal with contamination
-Use an airtight suit because this means that the radioactive atoms can not get inside the person
-people dealing with radiation leaks
67
Explain a method of protection when dealing with irradiation,
And mention which type if people may use this
Use a lead lined suit
So that the radiation can be absorbed by the suit, which could otherwise hit the person
Often used when getting an x ray
68
Sources with ….. half-life’s present a greater risk with irradiation because…
And sources with …. Half life present a greater risk with contamination because..
Short, because they have a higher activity so a higher rate of radioactive emissions
Long, because they will stay active for longer so need longer care and control, eg storgage
69
Give four methods that can be used to protect oneself against irradiation when dealing with radioactive sources
-wear a lead lined suit
-wear gloves and use tongs to keep it a safe distance away
-make sure the source is stored in a lead lined container
-limit the amount of time you are exposed to it to
70
Explain which type of radiation is most dangerous outside the body and which is not and why
Beta and gamma radiation are the most dangerous because they are partially and highly penetrating so can penetrate through the skin
Alpha is weakly penetrating
and can be stopped by dead skin cells
and can by stopped by a short distance of air
71
Explain which type of radiation is most dangerous inside the body and why
Alpha is most dangerous because it is strongly ionizing so can mutate cells or damage them
Beta and gamma are least dangerous because they are weakly ionizing
72
Explain why ionizing radiation is dangerous to humans, discussing the two main possible things that can happen
Dangerous because can either damage dna, killing the cells
Or can mutate the dna, which if replicated, can form a tumor, leading to cancer
73
Give two other possible things that can happen if a person has acute radiation exposure
Can cause skin burns
Can reduce amonts of white blood cells making you more prone to infection
74
Give four precautions when dealing with radiation
-wear protective clothing such as lead lined suits or airtight suits
-when not in use, store radioactive sources in lead lined containers
-keep a safe distance from the source by using gloves and tongs
-limit the amount of time of exposure to the radioactive source,
75
How can you monitor the amount of dosage of radiation that you receive, and what does this measure the dosage of radiation received in
Use a dosemeter
Which measures dosage of radiation in Sieverts
76
Explain why and how substances with a long half life should be treated
Sources with a long half life remain active for longer and so decay at a slower rate
This means that they are often buried underground to prevent radioactive emissions from being released into the environment
77
Definition of nuclear fission
The splitting up of large and unstable nuclei into smaller nuclei, releasing large amounts of energy
78
What are the two ways that nuclear fission can occur, and describe them
Spontaneous fission:
-when no additional energy is required for the fission to occur
-but is rare
Absorbing a neutron:
-when a neutron must be added so that it can be absorbed by the large and unstable nuclei
-so that it becomes more unstable and decays immediately
79
What are the two characteristics that a nuclei must have inorder for it to undergo nuclear fission
Must be large
Must be unstable
80
State two characteristics that the daughter nuclei have
They are lighter than the original nuclei
They are also radioactive
81
Why are …. Moving neutrons used in nuclear fission to make the nuclei unstable and decay
Slow
Because they are more easily absorbed by the nuclei
82
Explain how nuclear fission occurs
1)a slow moving neutron is fired at a large and unstable nuclei such as Uranium-235
2)This uranium nuclei absorbs this neutron, but the addition of the new neutron makes the nuclei more unstable
3)this causes it to split into two daughter nuclei and along with this, two or three neutrons are also released
4)these neutrons then go onto hit another uranium-235 nuclei, causing it to split apart and the process continues, this is called a chain reaction
5) with every fission reaction, gamma rays are released,
Aswell as large amounts of energy, which is then later transferred from nuclear potential energy to kinetic energy where using a nuclear power station, is converted into electrical energy
83
State the energy stores involved in the energy emitted from nuclear fission inorder to generate electricty
Energy is transferred from nuclear potential energy to kinetic energy
And then using a nuclear power station is transferred into electrical energy
84
What is a chain reaction
Process in nuclear fission, where neutrons released go onto hit another large and unstable nuclei causing it to split into more smaller nuclei and more neutrons, where this fission process continues onto another nuclei. The process repeats and this is the chain reaction
85
What is the function of a nuclear reactor
To control the chain reaction
So that the energy released from nuclear fission can safely be harnessed
And then used to make electrical energy in a nuclear power plant
86
Function of the control rods
To absorb neutrons to limit the rate of fission occurring
87
Explain how the control rods work
They are adjusted lower or higher so that for every 2 or 3 neutrons released from a fission reaction, only one neutron goes on to produce further fission reactions
88
How can you shut the nuclear reactor completely down
Lower the control rods all the way so that all the neutrons are absorbed and no more fission can take place
89
What happens if you lower the control rods deep
More neutrons are absorbed so the rate of fission decreases
90
What happens if you only lower the control rods a small amount
Then only a small amount of neutrons will be absorbed so the rate of fission increases
91
What are the control rods made of
Boron because able to absorb neutrons easily
92
What is the function of the fuel rods
They are where the fission reactions take place
93
What is the function of the moderator
To slow the neutrons down so that they can be more easily absorbed by U-235 in the fuel rods
94
Explain how the moderator works
Fast moving neutrons produced by fission, collide with the molecules in the moderator, which slows them down as they lose momentum
They reach thermal equilibrium with the moderator and so the neutrons are now called thermal neutrons
They can now be more easily absorbed by the U-235 in the fuel rods
95
What is the moderator made of
Graphite
96
What is the purpose of shielding in a nuclear reactor, and what two materials is it made of
To absorb the harmful ionizing radiation
Made of steel and concrete
97
What is the function of the coolant
It absorbs and transmits the heat energy produced in fission
Which is then used to turn water into steam
Where this steam is used to turn a turbine
Which is used to turn a generator
Which generates electricity
98
Give three advantages of using nuclear energy
-reliable because not dépendant upon the weather
-it is clean, so does not produce any green house gases
-less nuclear fuel would be required for the amount of fossil fuels required for the same amount of energy
99
Give three disadvantages of using nuclear energy
-expensive to decommission
-difficult and expensive to dispose of the radioactive waste released as it must be buried underground
-risk of major disaster such as radiation leak
100
Why is fusion really difficult to achieve
Inroder for the two nuclei to fuse, they must get close together
Which is difficult because they repel each other due to similar charges
So to overcome this they need to be travelling at really high speeds, so have to have high kinetic energy
To do this This requires really high temperatures and pressures
101
What is nuclear fusion
The process where two light nuclei join together to form a heavier nucleus
102
Why does nuclear fusion only occur in stars
Because it requires extremely large amounts of temperature and pressure
103
Explain why nuclear fusion creates such large amounts of energy
Because some of the mass of the original two nuclei are converted into energy, rather than being transferred to the helium nucleus
104
The energy produced from a fusion reaction can be calculated using what equation?
And state what each variable means
E=MC^2
E=total amount of energy released from fusion
M= mass converted into energy
C=speed of light
105
State and describe the three conditions required for fusion to occur
Must have very high temperatures
Must have very high densities/ pressures inorder to increase the possibility of collisions
Nuclei must be traveling at very high speeds with large amounts of kinetic energy inorder to overcome forces of repulsion
106
Name two common fuels used in nuclear fission
Uranium or plutonium isotopes
107
If fusion were possible, give three advantages it would have over fission
1)would produce more energy
2)fuel would be more plentiful than uranium and plutonium
3)would be safer because less radioactive waste produced
108
Describe the structure of the atom
It has a positively charged nucleus made up protons and neutrons.
And then it has electrons that orbit the nucleus
109
Give the relative masses of the subatomic particles of an element
Proton: 1
Neutron:1
Electron 1/1835
110
What types of radiation are ionizing
Alpha
Beta
Gamma
(Not neutron radiation)
111
In which process does a neutron turn into a proton and emit a fast moving electron
Beta decay
112
What effect does beta decay have on the mass number and at atomic number of an element
Atomic number increases, because during beta decay, a neutron changes into a proton, so it thus has one more proton
The mass number stays the same because the overall number of protons and neutrons is the same(as it has gained a proton but lost a neutron)
113
When are gamma rays released form an atom
When an atom decays and releases alpha or beta, there is still some excess energy that needs to be released
So is released in the form of gamma
And gamma always happens alongside alpha and beta, never alone
114
Is long half life more dangerous or short half life
Long half life because this means that it will remain radioactively active for longer
So more dangerous
115
What precautions are taken to reduce harm to both patients and doctors when using radioactive decay
Both wear protective clothing such as lead suits
Given radiation with a short half life, so that although the initial levels will be high enough to detect, it has a short activity so will dissapear from the patients body
116
Give a way that you can treat tumours internally, and then externally, and mention the type of radiation used
Internally, using medical tracers, which often use beta or gamma radiation
117
How is electricity generated in a nuclear power station
Nuclear fission reactions release nuclear energy
This is converted to thermal energy
This thermal heat energy is then used to turn water into steam
Steam is used to turn a turbine
Turbine is used to turn a generator
Generator e generates electricity in a nuclear power station
118
What is the type of energy released in a fission reaction
Kinetic energy
119
In terms of neutrons, how is nuclear fission controlled
Control rods absorb neutrons
To limit the rate of fission
So that for every two or three neutrons, only one neutron goes on to cause a fission reaction
120
When doing an experiment to investigate radiation, materials of various thickness will be used.
How do you know which material is the best absorber of radiation, by looking at the count rate of the sources used with it
The material which has the lowest count rate
Because this means that the least amount of radiation was able to penetrate through and be detected by the detector
Meaning it was absorbed by the material
121
Give two reasons why you should use substances with a …. Half life when investigating radiation
Long
Because a longer half life means less activity, so they will be less hazardous
Because the count rate is more likely to be constant and so will not need to be constantly replaced (bc remeber that radioactive decay is a random process, so if it takes longer to decay, that means that probability that it will completely decay is less)
122
Granite is a rock.
It contains a radioactive isotope of uranium that decays very slowly.
(i) Explain how scientists can use this radioactivity to find the age of a piece of granite.
thereisaknownproportion/composition/ activity when rocks formed; any FOUR from:
MP2. measure/determine the proportion of
uranium or the activity now;
MP3. compareactivitynowtooriginalactivity/eq;
MP4. (hence)determinethetime/numberof half-lives elapsed;
MP5. (hence)calculateagefromreferenceto half-life;
123
Why is shielding required (3)
Because the waste released from the nuclear reactor is radioactive
So it absorbs hazardous ionizing radiation
Which can damage cells and mutate dna, causing cancer
124
Definition of unstable
The ability to decay and emit radioactive particles such as alpha or beta, or they emit gamma
125
There are two sources of alpha radiation in some houses:
radon gas in the air
solid americium in a smoke alarm
The alpha particles from radon are a greater risk to health than the alpha particles
from americium.
Explain why, giving two reasons
Because radon gas is a gas and is mobile
Americium is a solid so stays in the smoke alarm
Radon can escape and be inhaled and damage internal tissue
Americium are absorbed by the smoke detector
126
Which out of the three electromagnetic radiations has the highest speed
Gamma rays
127
What effect does the emission of a beta particle have on a nucleus
Neutron changes Into a proton
Therefore neutron number decreases by 1
Neutron changes into a proton
Therefore proton number increases by
128
Describe a method to find the corrected count rate (4 marks)
-move source far away from detector
-measure background radiation for a specific amount of time by observing count rate
-repeat three times and take an average
-minus new count rate from old count rate to find corrected count rate
129
Why is it important that the control rods are not lifted too high
Because then less neutrons will be absorbed
So the rate of the fission reaction will be too high
So it will emit amounts of energy that are extremely large
Which could lead to a meltdown of the reactor
130
A scientist wants alpha particles to hit a screen, so he removes the air from the container he does this in.
Explain why he does this
Because alpha particles have a short range(short penetrating power) in air
So would not be able to reach the screen
131
What are the three things Rutherford found from his gold leaf experiment
-some alpha particles went straight through, meaning an atom is mostly empty space
-some were deflected a small amount, meaning the atom constats of protons, positively charged
-some bounced right back
132
Explain why alpha particles are less penetrating than beta (4)
Have larger mass, bc helium nucleus, so ram of 4,
But beta has mass of 1/1800
So alpha can collide more readily with other atoms, making it difficult to penetrate through
Alpha particles also have a higher charge and are more ionizing
133
Explain why if a radioactive isotope with a long half life is absorbed by the body, that this is dangerous
Because long half life means that it stays active for longer
So decays at a slower rate
Therefore all of the radiation emitted by it will be absorbed by the bones and can
Be hazardous, eg damaging cells or mutating dna creating a tumour, causing cancer
134
Explain why strontium-90 and yttrium-90 can both be described as isotopes, even though they have different numbers of protons.
Because they are isotopes of different elements
Therefore strontium will have same number of protons as other strontium atoms
And yttrium will have some number of protons as otehr ytrriuk atoms
135
Explain why beta radiation is good for treating cancer with internal methods
Less penetrating than for example gamma, so can not travel outside the body
And is absorbed by the tumor
And reduces risks to Damaging and killing other healthy cells
136
Give the nucleon number, and the proton number of a neutron
Nucleon= 1
Mass=0
