P6

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  • Created by: Jess
  • Created on: 15-05-13 18:52
What is the nucleus of an atom made up of?
The nucleus of an atom contains protons and neutrons?
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What is on the outside of an atom?
Electrons
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Why do some atoms have unstable nucleus'?
Because the isotopes tend to be radioactive, so the nucleus decays and emits radiation
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What does it mean for an element to be radioactive?
It means that the element emits ionising radiation all the time
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Why are radioactive atoms unstable?
Because they decay to try to make themselves more stable
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Why can you not predict when unstable atoms will decay?
Because unstable atoms decay randomly and are completely unaffected by physical conditions e.g. temperature or chemical processes e.g. bonding
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What are the 3 types of ionising radiation?
alpha, beta, gamma
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What is ionisation ?
Ionisation is where ionising radiation can transfer enough energy to break an atom or molecule into ions
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What are alpha particles like?
Alpha particles are big, heavy and fairly slow moving. This means that alpha particles don't penetrate into many materials and are released by a very heavy nuclei e.g uranium.
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What is an alpha particle made up of?
An alpha particle is a helium nucleus made up of 2 protons and 2 neutrons
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Describe a beta particle
Beta particles are quite fast and small. They penetrate moderately into materials before they're stopped, and are released by nuclei that have too many particles
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What happens to a neutron in beta decay?
The neutron in beta decay turns into proton, so the element changes, and a beta particle is emitted
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What is a beta particle identical?
A beta particle is identical to an electron and has virtually no mass and a charge of -1
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What is gamma radiation?
Gamma radiation is an electromagnetic wave that has no mass
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When is gamma radiation emitted?
After spitting out an alpha or beta particle, the nucleus might need to get rid of some extra radiation which it does by emitting a gamma ray
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What are alpha particles blocked by?
Paper
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What are beta particles blocked by?
Aluminium
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What are gamma rays blocked by?
Thick lead
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What is a half-life?
Half-life is the time taken for half of the radioactive nuclei now present to decay
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What happens as a radioactive source gets older?
The older a radioactive source is the less radiation it emits, as the more unstable nuclei decay, the radioactivity of the source as a whole decreases
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What is the difference between a short half-life and a long half-life?
A long half-life means that the activity falls more slowly because most of the nuclei don't decay for a long time, and a short half-life means that the activity falls quickly as lots of the nuclei decay in a short time
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How did Rutherford show that atoms have a positive nucleus?
They fired alpha particles at thin gold foil most of the particles went through but a few of them bounced back. This meant that the nucleus had to have a +ve charge or the +vely charged alpha particles wouldn't have been repelled by the nucleus
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How is the nucleus of an atom held together?
The nucleus is held together by strong force
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What is strong force?
Strong force is a strong attractive force that holds the nucleus together, and is stronger than the repulsive electrostatic force between protons in the nucleus (which repel each other) but strong force only works at short range 0.000000000000001m
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What is nuclear fusion?
Nuclei fusion is when two nuclei fuse to create a larger nucleus, releasing energy as they do so
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How do nuclei fuse together?
Nuclei can only fuse together if they overcome the repulsive electrostatic force and get close enough together for strong force to hold them together, for this you need lots of energy ergo high temperature
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What happens to mass when nuclei undergo nuclear fusion/fission?
When nuclei undergo nuclear fission/fusion they lose mass and energy is released (E=mc2). This is because according to Albert Einstein mass is a form of energy, therefore it can be converted into other forms of energy.
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How do nuclear power stations release energy?
Nuclear power stations release energy by splitting atoms. They do this by making a nuclear fuel (e.g. uranium) undergo nuclear fission which starts when neutrons are fired at the fuel, causing some large unstable nuclei to split into 2 smaller nuclei
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Roughly, how many neutrons are released with each split?
Each split nucleus releases 2 or 3 more neutrons (and lots of energy)
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What is nuclear fission?
Nuclear fission is where atoms split apart which releases energy. Nuclear fission is the opposite of nuclear fusion.
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How much more energy does nuclear fission with 1 gram of uranium release than 1 gram of oil?
10 000 times more
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How do you deal with 'low level' waste?
Low level waste that is considered slightly radioactive (e.g. paper towels, gloves) can be disposed by burying in secure landfill sites
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How do you deal with 'immediate level' waste?
Immediate level waste (e.g.metal cases of used fuel rods) is usually quite radioactive is sealed in concrete blocks then put in steel canisters for storage
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How is 'high level' waste dealt with?
High level waste is so radioactive it generates lots of heat. This waste is sealed in glass and steel, then cooled for 50 years before being moved to permanent storage
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Why is it difficult to find places to bury high and immediate level waste?
The site has to geologically stable, since big rock movements could break the canisters and the radioactive material could leak out, even if geologists do find suitable places, people nearby often object
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What could a high dose of ionising radiation cause in a human?
A high dose of radiation tends to kill cells outright, causing radiation sickness
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What could a lower dose of ionising radiation cause in a human?
Lower doses of radiation tend to damage cells without killing them which could cause cancer
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What is irradiation?
Irradiation is being exposd to radiation without coming into contact with the source. The damage to your body stops as soon as you leave the radioactive area.
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What is contamination?
Contamination is picking up some radioactive material e.g. breathing it in; eating it; drinking it; getting it on your skin. You will still be exposed to the radiation once you have left the radioactive area
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What are radiation doses measured in?
Sieverts (Sv) or millisieverts (mSv)
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What is the typical amount of background radiation experienced by everyone a year?
2mSv
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Which people are categorised into high risk of radiation exposure?
uranium miners; workers in nuclear power plants; radiographers; miners; airline staff
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How are high risk people in the UK monitored?
Their does of radiation are monitored and have regular check ups to make sure they're not getting sick because of the radiation they have been exposed to at work
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Where does low level background radiation come from?
Natural radioactive elements (e.g. air, soil, rocks); space (cosmic rays, mainly from the Sun); human activity (from nuclear explosions and waste from nuclear power plants)
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When are radioactive sources considered to be 'safe'?
Radioactive sources are considered 'safe' when the radiation they are emitting is at the same level as background radiation
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How can ionising radiation be helpful?
treating cancer; sterilising medical equipment; sterilising food; detecting diseases using tracers
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How is ionising radiation used in treating cancers?
Since high doses of gamma rays will kill any living cells, they can be directed carefully and at the right dosage can kill caner cells, without damaging too many normal cells
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How can ionising radiation be used in sterilising medical equipment?
Gamma rays sterilise medical instruments by killing microbes this is better boiling plastic instruments that would be damaged by the high temperature. You need to use a strongly radioactive source that has a long half-life so it doesnt need replacing
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How is food sterilised with ionising radiation?
Food is sterilised with gamma rays by killing all microbes, this keeps the food fresh for longer without needing to freeze or cook it. The food is not radioactive after having gamma rays passed through it, so it's still safe to eat.
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What are tracers?
Tracers are radioactive molecules that can be injected into people, that make their way around people's bodies followed by an external detector
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What is the purpose of tracers?
Tracers can detect cancer or whether an organ in working properly
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What type of isotope must tracers be?
Isotopes used as tracers must be gamma or beta emitters so they pass through the body quickly, with short half-lives as the radioactivity inside the patient should disappear quickly
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Other cards in this set

Card 2

Front

What is on the outside of an atom?

Back

Electrons

Card 3

Front

Why do some atoms have unstable nucleus'?

Back

Preview of the front of card 3

Card 4

Front

What does it mean for an element to be radioactive?

Back

Preview of the front of card 4

Card 5

Front

Why are radioactive atoms unstable?

Back

Preview of the front of card 5
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