P6

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  • Created by: Faith16
  • Created on: 30-03-16 12:42
What is an atom mostly made up of?
Empty space
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What is an isotope?
Atoms with the same number of protons but different number of neutrons
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What are two common isotopes of carbon?
Carbon-14 (unstable) and carbon-12 (normal)
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Why are some isotopes radioactive?
Because of the nucleus being unstable so it decays (breaks down) and emits radiation
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Why do some elements emit ionising radiation?
As they are unstable and try to decay to make themselves more stable
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Are unstable atoms affected by physical conditions?
No, the decay happens at random
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What three types of ionising radiation do atoms produce when decaying?
Alpha, beta and gamma
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Describe an alpha particle.
They are relatively big and heavy and slow moving- don't penetrate far into materials
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What are alpha particles released from?
A very heavy nuclei such as uranium
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What are alpha particles made up from and what is their mass and charge?
Made up from helium nucleus (2 protons and 2 neutrons). They have a mass of 4 and a charge of 2
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Describe an beta particle.
Move quiet fast and are small, penetrate moderately into materials before they are stopped.
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What are beta particles released from?
A nuclei that has too many neutrons (neutron in the nuclei turns into a proton so the element changes and a beta particle is emitted)
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What is the mass and charge of a beta particle?
They have virtually no mass and a charge of -1
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How is gamma radiation produced?
When an nucleus needs to get rid of some energy (since it is just energy it doesn't change the element of the nucleus)
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What is a gamma ray a type of?
Electromagnetic wave
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Describe a gamma ray.
Can penetrate a long way into material without getting stopped and it has no mass.
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What blocks the three types of radiation?
Alpha blocked by paper. Beta blocked by thin aluminium. Gamma blocked by thick lead
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What is half-life?
The time taken for half of the radioactive nuclei now present to decay
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What happens when a nuclei decays?
It becomes less radioactive
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How does the time taken to decay vary for different isotopes?
Some take just a few seconds where as others take millions of years
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What is the problem with trying the measure decay?
The activity never reaches zero which is why we have the idea of half-life to measure how quickly the activity decreases
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What does a short half-life mean?
The activity falls quickly because lots of the nuclei decays in a short time
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What does a long half-life mean?
The activity falls more slowly because list if the nuclei doesn't decay for a long time
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What did Rutherford discover when firing alpha particle (positive) at a thin gold foil?
Most went straight through but the odd one came back- he discovered only a small mass of the atom has a tiny nucleus and the rest is empty space (nucleus must be positive to repel the odd alpha particle)
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What is the nucleus held together by?
Repulsive electrostatic force which is called the strong force
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Why does the nucleus have to be held together by a strong force?
Because it contains positively charged protons which repel each other but the force only has a short range so with large separations between particles the force is weak so it will effectively disappear
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What is nuclear fusion?
When two nuclei combine (fuse) to create a larger nucleus which produces energy when they do
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Why do you need high temperatures for nuclear fusion?
As the nuclei can only fuse if they overcome the repulsive electrostatic force and get close enough for the strong force to hold them together
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What happens when nuclei undergo nuclear fusion or fission?
They loss mass and energy is released
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What is nuclear fission?
Where the atoms are split apart
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How does nuclear fission take place in a nuclear power station?
Neutrons are fired at the nuclear fuel (uranium or plutonium) causing some of its large, unstable nuclei to split into two smaller nuclei then it is repeat again and again
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Why are nuclear reactions different to chemical reactions (e.g. burning)?
They release a lot more energy
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How is nuclear fission carefully controlled?
The uranium fuel used in the nuclear reactors is contained in the fuel rods (capture neutrons and emit neutrons when the nuclei split), control rods absorb some neutrons to slow down reaction, coolant (e.g. water) takes away the heat.
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Why does the chain reaction in the reactor have to be controlled?
Because the reactor would overheat
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What are the 3 different levels of waste and how are they dealt with?
Low level- burying in secure landfill site. Intermediate level- sealed in concrete blocks and put in steal canisters. High level- sealed in gas and steel then cooled for 50 years before moved to permanent storage
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Why is intermediate level waste normally kept on site?
As if there was an earthquake the radioactive waste could leek out and if it is buried locally, local people object
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How does ionising radiation damage living cells?
High doe of radiation kills cells outright causing radiation sickness where as lower doses damage cells without killing them which causes cancer
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What is irradiation?
Being exposed to radiation without coming in contact with the source, damage to body stops as soon as you leave the area
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What is contamination?
Picking up some radioactive material e.g. breathing it in, drinking contaminated water or getting it on your skin (still exposed after you have left the area)
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What is radiation dose measured in?
Sieverts (Sv) or millisieverts (mSv)
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What is the typical amount of background radiation?
2 mSv/year
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What categories of people are at higher risk of radiation exposure?
Uranium miners and processors, workers in nuclear power plants, airline staff (cosmic waves), miners (rocks naturally radioactive), some medical staff (e.g. radiographers) and nuclear researchers
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What is background radiation?
Low level radiation that is constantly irradiating and contaminating us
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What are the different kinds of background radiation?
Natural- air,soil, living things and rocks (radon gas). Space- cosmic rays. Human activity- nuclear explosions or waste from nuclear power plants
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How is ionising radiation useful?
Treating cancer- gamma radiation kill cancer cells. Sterilising medical equipment- gamma rays kills microbes (if boiled may be damaged at high temperatures). Sterilising food-kill microbes, fresher for longer. Detecting diseases using tracers
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How can you detect diseases using tracers?
Radioactive molecules are injected into people and followed around body using external detecter. Detect cancer or if an organ if working. Must be gamma or beta (can pass out of body), must have short half-life
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Other cards in this set

Card 2

Front

What is an isotope?

Back

Atoms with the same number of protons but different number of neutrons

Card 3

Front

What are two common isotopes of carbon?

Back

Preview of the front of card 3

Card 4

Front

Why are some isotopes radioactive?

Back

Preview of the front of card 4

Card 5

Front

Why do some elements emit ionising radiation?

Back

Preview of the front of card 5
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