P7 RADIOACTIVITY
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- Created by: 15cstone
- Created on: 03-03-19 11:38
What changes in both alpha and beta decay?
the number of protons in a nucleus changes
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What changes in alhpa decay?
the number of protons and neutrons in a nucleus
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Relative mass and relative charge of a proton?
RM - 1 RC - +1
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Relative mass and relative charge of a neutron?
RM 1 RM 0
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Relative mass and relative charge of an electron?
RM 0 RC -1
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Wat is the atomic number of a nucleus?
number of protons
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Mass number of a nucleus?
number of protons and neutrons
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What are isotopes?
atoms of the same element with different number of neutrons
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What is an alpha particle made up of?
two protons and two neutrons
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Relative mass and relative charge of alpha particle?
RM 4 RC +2
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What is an alpha particle identical to?
helium nucleus
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What happens to its atomic number when an unstable nucleus emits an alpha particle?
goes down by 2
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What happens to the mass number of an unstable nucleus when it emits an alpha particle?
it goes down by 4
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What happens to the mass and charge of an unstable nucleus when it emits an alpha particle?
both reduced
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What is formed when the thorium isoptope (mass number -228 / atomic number-90) when it emits an alpha particle?
a radium isoptope (mass number-224 / atomic number - 88)
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What is a beta particle?
an electron
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What nuclei emit beta radiation?
a nucleus that has too many neutrons compared with its protons
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What happens to a neutron in the nucleus before beta radiation is emitted
it changes into a proton and a beta particle
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What happens to the electron which the neutron changes into?
it is instantly emitted from the nucleus
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Relative mass and relative charge of a beta particle?
RM 0 RC -1
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What happens to the atomic number of an unstable nucleus when it emits a beta particle?
goes up by one
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What happens to the mass number of an unstable nucleus when it emits a beta particle?
stays the same
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What happens to the charge and the mass of an unstable nucleus when it emits a beta particle?
charge is increased, mass is unchanged
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What forms when a potassium isotope (mass number - 40 / atomic number - 19) when it emits a beta particle?
nucleus of calcium isotope (mass number - 40 / atomic number 20)
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What is a gamma ray?
electromagentic radiation from the nucleus of an atom
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Charge and mass of gamma rays?
uncharged and no mass
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What are neutrons emitted by some radioactive substances a result of?
alpha particles colliding with unstable nuclei in the substance
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How many more protons and neutrons are in uranium-238 compared with radium-224 (refer to periodic table)
4 more protons and 10 more neutrons
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What is alpha radiation stopped by?
paper
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What is the range of alpha radiation?
a few centimetres
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What is beta radiation stopped by?
a thin sheet of metal
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What is the range of beta radiation in the air?
about one meter
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Compare the ionising radiation of beta radiation to alpha and gamma radiation?
less ionising than alpha radiation and more ionising than gamma radiation
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What is gamma radiation stopped by?
thick lead
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What is the range of gamma radiation?
unlimited
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What does alpha, beta and gamma radiation do to substances they pass through?
ionises the substances
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What is used to find out how far each type of radiation travels through the air?
Geiger counter
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What can the radiation from a radioactive substance do to atoms
Knock electrons out of atoms
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What is this called?
ionisation
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What happens to the charge of the atoms and why?
they become charged because they lose electrons
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What happens when an object is exposed to ionising radiation?
it is said to be irritated
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Do ionised substances become radioactive?
no
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What is radioactive contamination?
the unwanted presence of materials containing radioactive atoms on other materials
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What is the hazard from contamination due to?
the decay of the nuclei of the contaminating atoms
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What is a charged particle?
an ion
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What can ionisation in a living cell do?
damage or kill the cell
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Why is this?
because alpha radiation has the greatest ionising power
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Worker who use onising radiation reduce their exposure by...
2, 4, 5
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What do smoke alarms contain?
a radioactive isotope that sends out alpha particle into a gap in a circuit in the alarm
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What do the alpha particles do and why?
ionise the air in the gap so there is a current across the gap
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What happens in the smoke alarm when there is a fire?
smoke absorbs the alpha particles, preventing them ionising the air
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Why can't beta or gamma radiation be used in smoke alarms?
they do not create enough ions to make the air in the gap conduct electricty
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What radiation is used in smoke alarms?
alpha
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What is the activity of a radioactive source?
the number of unstable atoms in the source that decay per second
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What is the unit of activity?
Becquerel (Bq)
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Why does the activity of samples decrease as the nucleus of each unstable atom decays?
because the number of parent atoms decreases
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What is the count rate?
the number of counts per second
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The half-life of a radioactive isotope is the averge time it takes:
1 & 2
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Is radioactive decay a random process?
yes
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If you said 'yes', what does this mean?
no-one can predict exactly when an individual atom will suddenly decay
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Can you predict how many atoms will decay in a given time?
yes
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If you chose 'yes', why is this?
because there are so many of them
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Suppose you start with 1000 unstable atoms and 10% decay every hour, how many decay after two hours?
190 atoms
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What is the half-life of a radioactive isotope?
the avergae time it takes for the number of nuclei of the osotope in a
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What happens to the number of atoms of a radioactive isotope every half-life?
it decreases
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The count rate after n half-lives =
the initial count rate / 2^n
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How is nuclear radiation used in medicine?
1 & 2
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What is the use of radioactive tracers?
to trace the flow of a substance through an organ
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What does a radioactive tracer contain and why?
a radioactive isotope that emits gamma radiation as it can be detected outside the system
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What do doctors use to find out if a patient's kidney is blocked?
a radioactive iodine
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What does a patient do before having their kidney's tested with a radioactive iodine?
a drink of water containing a tiny amount of the radioactive substance
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What is then placed against each kidney?
a detector
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What does the radioactive substance do to the normal kidney?
it flows in and out of the normal kidney
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What does the radioactive substance do in the blocked kidney?
it goes into the kidney but doesn't flow out
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Why is radioactive iodine used to test a patient's kidneys t see whether they are blocked?
all three
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What is the use of gamma cameras?
to take images of internal body organs
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What happens before an image is taken using the gamma camera?
the patient is injected with a solution that contains a gamma-emitting radioactive isotope
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What is the gamma-emitting radioactive isotope absorbed by?
the organ being tested
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What detects the gamma radiation emitted by the solution?
a nearby gamma camera
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What do the gamma rays then pass through?
the holes in the thick lead grid in fron tof the detector
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What radiation is used to destroy cancerous tumours?
gamma
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Why is gamma radiation used to destroy cancerous tumours?
because it can penetrate deeper into the body than beta and alpha radiation
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What is the use of radioactive implants?
to destroy cancer cells in some tumours
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What are the half-lives of the isotopes that permanent implants use?
1- isotopes with half-lives long enough to irradiate the tumour over a given time
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What is background radiation?
ionising radiation from radioactive substances in the environment
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Percentage of backgroundradiation from the ground.
14%
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Percentage of background radiation from food and drink.
11.5%
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Percentage of background radiation from cosmos.
10%
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Percentgae of background radiation from the air (radon).
50%
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Percentage of background radiation from medicine.
14%
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How useful a radioactive isotope is depends on:
1, 3,
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What is released when a nucleus undergoes fission?
2 & 4
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What is nucleur fission? (What are the products?)
the spllitting of an atom's nucleus into two smaller nuclei and the relase of two or three neutrons and e
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What is a chain reaction?
a reaction in which one reaction causes further reactions, which in turn cause further reactions...
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How does nucleur fission cause a chain reaction?
a fission event releases neutrons, which can cause another fissionable nuclei to split
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What makes sure that energy is released at a steady rate in a nucleur fission reactor?
exactly one fission neutron from each fission event goes on to produce more fission
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What do most reactors use as their fuel?
enriched uraium
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What does a nucleur reactor have spaced in the reactor core?
uranium fuel rods
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What does the rector core contain
all of them
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What slows down the fission nuetrons?
collisions with the atoms in the water molecules
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Why do the neutrons need to be slowed down in the nuclear reactor?
because fast neutrons don't cause further fission of U-235
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How does the water act as a moderator?
because it slows down the fission neutrons
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What does fission mean?
splitting
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What do the control rods in the core do?
both
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The fuel rods become very _______ and the water acts as a ______.
hot / coolant
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What is the reactor core in and why?
a vessel made of thick steel to withstand the very high temperature and pressure in the core
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What is the thick steel vessel of the reactor core enclosd by?
thick concrete walls
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What is nuclear fusion?
the process of forcing the nuclei of two atoms close enough thogether so that they form a single larger nucleus
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How is nuclear fusion brough about?
by making two light nuclei collide at very high speed
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What happens to some of the mass of the small nuclei in nuclear fusion?
it is converted to energy
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What is some of the energy made by nuclear fusion transferred as?
nuclear radiation from the large nucleus that is formed
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The Sun is about __% hydrogen and __% helium
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What is the core of nuclear fusion reactors made up of?
a plasma of bare nuclei with no electrons
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What does fusion mean?
joining together
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What is formed when two protons fuse together?
a 'heavy hydrogen' nucleus
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Why does the plasma of light nuclei need to be heated to high temperature and pressures?
or else the nuclei will not fuse
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Why do the nuclei in a fusion reactor need to be at high temperatures and pressures?
if the nuclei are moving fast enough, they can overcome this force of compulsion and fuse together
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Why do the nuclei in the fusion reactor repel each other?
because of their positive charges
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What is the plasma in a fusino reactor contained by?
a magnetic field
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Why is the plasma contained by a magnetic field?
so it doesn't touch the reactor walls and go cold
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Is the fuel for fusion reactors easily availabe?
yes
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Why is the fuel for fusion reactors easily available?
because heavy hydrogen is naturally present in sea water
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The energy release in fusion reactors could be used to generate _____.
electricity
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What do fission reactors produce?
nuclear waste
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What reactions take place in the Sun's core?
fusion reactions
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Where does radon gas come from (naturally)?
seeps through the ground from radioactive substances in rocks deep underground
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What radiation does radon gas emit?
alpha
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Other cards in this set
Card 2
Front
What changes in alhpa decay?
Back
the number of protons and neutrons in a nucleus
Card 3
Front
Relative mass and relative charge of a proton?
Back
Card 4
Front
Relative mass and relative charge of a neutron?
Back
Card 5
Front
Relative mass and relative charge of an electron?
Back
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