P6 Revision.

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  • Created by: ElishaG
  • Created on: 16-06-16 17:12
Describe the nucleus.
1)Nucleus contains protons and neutrons.2)it's where most of the mass of an atom is.3)It's positively charged.4)It is tiny.
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Describe electrons.
1)Electrons are very small.2)Go around nucleus.3)Negatively charged.4)Lot of space in between shells-this gives atoms their overall size.
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What are isotopes?
Atoms with the same number of protons but a different number of neutrons.
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Give an example of a stable isotope.
Carbon 14.
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Give an example of an unstable isotope.
Carbon 12-it emits radiation.
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What do radioactive elements emit?
Ionising radiation.
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Describe radioactive atoms.
1)Some elements emit radiation all the time.2)Radioactive atoms are unstable-decay themselves to be more stable.3)Unstable atoms randomly decay-can't predict it.4)When it decays, spits out one or more of the 3 ionising radiations.
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What are the 3 types of ionising radiation?
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What usually happens when the atoms decay?
The atom often changes into new element.
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What is ionisation?
Ionising radiation can transfer enough energy to break an atom or molecule into pieces called ions.
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What can the ions in ionising radiation then do?
Take part in other chemical reactions.
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Describe alpha radiation.
1)Particles are relatively big and heavy,quite slow.2)Stopped quickly by materials.3)Released by heavy nuclei e.g. uranium.4)Alpha particle is a helium nucleus-2 protons and 2 neutrons.Mass=4 charge=+2.
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Describe beta radiation.
1)Particles move quite fast and are quite small.2)Moderately stopped by materials.3)Released by nuclei with too many neutrons.4)During beta decay,neutron turns into proton-beta particle emitted.5)Beta=electron.6)Charge=-1.7)Not much mass.
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Describe gamma radiation.
1)After spitting out alpha or beta,nucleus may need to get rid of extra energy.2)Does this by emitting gamma rays.3)No mass.4)Can go long way though materials without being stopped.5)Gamma ray doesn't change element of nucleus that emits it.
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What can alpha radiation be blocked by?
Paper, skin.
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What can beta radiation be blocked by?
Aluminium,sheet of any metal.
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What can gamma radiation be blocked by?
Thick lead, very thick concrete.
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What happens to the radioactivity of something overtime?
It decreases.
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Why does radioactivity decrease over time?
1)Each time an unstable nucleus decays, it means there is one less radioactive nucleus.2)As more unstable nuclei decay,radioactivity decreases, so older a radioactive source is, the less radiation it emits.
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How long does it take for isotopes to decay?
Time varies a lot, for some isotopes it's a few seconds but for others it's millions of years.
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What is the problem with measuring radioactive decay?
The activity never reaches 0. So we use half-life to measure how quickly activity decreases.
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What is the definition of half-life?
The time taken for half of the radioactive nuclei now present to decay.
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What does a short half-life mean?
The activity falls quickly as lots of the nuclei decay in a short time.
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What does a long half-life mean?
The activity falls more slowly as most of the nuclei don't decay for a long time.
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Who showed that atoms have a positive nucleus?What year did they do this?
Ernest Rutherford in 1909.
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Explain what Rutherford did.
1)Tried to fire alpha particles(positively charged) at thin gold foil.2)Most alpha particles went straight through, some came straight back.
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What conclusions did Rutherford make from his experiment?
1)Most mass of atom is in centre.2)Rest of atom mostly empty space-which is why alpha went through.3)Nucleus positively charged-as alpha was repelled.
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How is the nucleus held together.
1)Contains protons which repel each other.2)Held together by strong force-which is much greater than electrostatic force.3)Strong force has short range.
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What is nuclear fusion?
Nuclei can fuse to create a larger nucleus,releasing energy when they do(called nuclear fusion)
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Explain why nuclei need to be brought close together to fuse.
1)Nuclei can only fuse if they overcome electrostatic force and get close enough for strong force to take over.Lot of energy needed.
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What does nuclear fusion do?
Converts mass into energy.
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How do nuclear power stations release energy?Explain how they do this
By splitting atoms.1)Nuclear fuel e.g. uranium or plutonium, releases lot of energy when nuclei split apart.2)Called nuclear fission and starts when neutrons are fired at fuel-causing large unstable nuclei to split-2 or 3 neutrons released+energy.
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What does nuclear fission release?
A lot of energy-more than chemical reactions e.g. burning. 1g of uranium is 20x 1g of oil.
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Explain nuclear fission
1)Chain reaction.2)Neutron splits a nucleus,releasing more neutrons.3)Fuel used in nuclear reactors is inside fuel rods.4)Rods capture and emit neutrons.5)Reaction has to be controlled or reactor would overheat.Continued...
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Nuclear fission continued..
6)Control rods absorb some neutrons to slow reaction rate-moved in and out of reactor to absorb more or less.7)Coolant e.g. water used to take away heat.8)Heat used to produce steam to turn turbine and generator to generate electricity.
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What is the main problem with nuclear power?
It produces radioactive waste.
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What are the three types of waste from nuclear power stations?
Low level, intermediate and high level.
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Give an example of low level waste and how it can be disposed of.
Paper,gloves etc. Buried in secure landfill site.
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Give an example of intermediate level waste and how it can be disposed of.
Metal cases of used fuel rods,hospital waste.Sealed in concrete blocks then in steel canisters for storage.
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How can high level waste be disposed of?
Sealed in glass and steel, then cooled for 50 years, then put in steel canisters.
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Why is it difficult to find suitable places to bury intermediate and high level waste?
Site has to be geologically stable e.g. no earthquakes as movements of rock could break canisters-causing a leak.People object to it.
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Explain how ionising radiation can damage living cells.
They can break molecules into ions.Ions can be very reactive and could cause serious damage to body cells.
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What do lower doses of radiation do?
Damage cells without killing them, which can cause cancer.
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What does a high dose of radiation do?
Kills cells outright-causing radiation sickness.
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What is irradiation?
Being exposed to radiation without coming into contact with the source.Damage to body stops when you leave radioactive area.
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What is contamination?
Picking up something radioactive e.g. breathing it in,drinking contaminated water or getting it on your skin.Will still be exposed when you leave radioactive area.
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What is radiation dose measured in?
Sieverts(Sv) or Millisieverts (mSv).
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Which people are at a higher risk of radiation exposure?
1)Uranium miners and processors.2)Nuclear power plant workers.3)Airline staff.4)Miners.5)Some medical staff.6)Nuclear researchers.
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What do people with a higher risk have to do?
Have to have radiation doses carefully monitored and have check-ups to make sure they aren't being exposed to too much radiation.
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Where does background radiation come from?
1)Natural radioactive elements in air, soil, rocks.2)Space(cosmic rays).3)Human activity e.g. nuclear explosions or nuclear waste.
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When are radioactive sources considered safe?
When the radiation they are emitting is the same level as background radiation.
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What are the used of ionising radiation?
1)Treating cancer.2)Sterilising medical equipment.3)Sterilising food.4)Detecting diseases using tracers.
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Describe how ionising radiation can be used to treat cancer
1)High doses of gamma radiation kill cells.2)Have to be directed carefully and at right dosage to kill cancer cells without damaging too many normal cells.3)Damage always done to normal cells-makes patient feel ill.
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Describe how ionising radiation can be used to sterilise medical equipment.
1)Gamma rays kills microbes.2)Better than trying to boil plastic-could be damaged.3)Need to use strongly radioactive source with long half-life.
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Describe how ionising radiation can be used to sterilise food.
1)Food can be sterilised same way as medical equipment.2)Keeps food fresher for longer,without having to preserve it.3)Food not radioactive afterwards, so is safe to eat.
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Describe how ionising radiation can be used to detect diseases using tracers.
1)Tracers are radioactive molecules that can be injected into people.External detector used to view progress around body.2)Isotopes used as tracers must be gamma or beta so radiation will pass out of body.3)Should have short half-life.
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Other cards in this set

Card 2


Describe electrons.


1)Electrons are very small.2)Go around nucleus.3)Negatively charged.4)Lot of space in between shells-this gives atoms their overall size.

Card 3


What are isotopes?


Preview of the front of card 3

Card 4


Give an example of a stable isotope.


Preview of the front of card 4

Card 5


Give an example of an unstable isotope.


Preview of the front of card 5
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