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31 Cards in this Set
- Front
- Back
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What does an atom consist of? |
A nucleus which contains protons and neutrons. This makes up most of the mass of the atom but takes up virtually no space. Small electrons which move around the outside of the atom, taking up a lot of space. |
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Isotopes |
Atoms with the same number of protons but different numbers of neutrons. Usually each element only has one or two stable isotopes and the other isotopes tend to be radioactive as the nucleus is unstable so it decays and emits radiation. |
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When do unstable atoms decay? |
At random and you can't predict what will happen as it is completely unaffected by physical conditions e.g. temperature. |
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Ionisation |
Ionising radiation can transfer enough energy to break an atom or molecule into bits called ions. |
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What are the three types of ionising radiation? |
Alpha Beta Gamma |
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Alpha radiation |
The particles are big, heavy and fairly slow-moving. They don't penetrate far into materials. They have a mass of 2 and a charge of +2. |
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Beta radiation |
The particles move quite fast and are quite small. They penetrate moderately into materials before they're stopped. A beta particle is identical to an electron, with virtually no mass and a charge of -1. |
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Gamma radiation |
It is an electromagnetic wave with no mass. They can penetrate a long way into materials without being stopped. |
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What blocks the three types of radiation? |
Alpha particles - paper. Beta particles - thin aluminium. Gamma rays - thick lead. |
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Half-life |
The time taken for half of the radioactive nuclei now present to decay. |
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Short half-life |
The activity falls quickly, because lots of the nuclei decay in a short time. |
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Long half-life |
The activity falls more slowly because most of the nuclei don't decay for a long time. |
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What did Rutherford's scattering show him? |
Most of the mass of a gold atom was concentrated at the centre in a tiny nucleus. The rest of the atom must be mainly empty space as most of the alpha particles went straight through the foil. |
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How did Rutherford know the nucleus had a positive charge? |
The positively charged alpha particles wouldn't be repelled by the nucleus or scatter. |
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What is the strong force? |
The force that means the nucleus doesn't fly apart because it's held together by it which is much greater than the repulsive electrostatic force between the protons. |
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What happens to the strong force at larger seperations? |
The strong force is so weak that it effectively disappears. |
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What is nuclear fusion? |
When two nuclei can combine (fuse) to create a larger nucleus, releasing energy when they do. |
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What do nuclei need to do in order to fuse? |
Overcome the repulsive electrostatic force and get close enough for the strong force to hold them together. For this you need lots of energy - which means a high temperature. |
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How can you figure out how much energy is released during fission or fusion? |
Energy (J) = mass (kg) x (speed)2 (m/s)2. |
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Nuclear fission |
When nuclear fuel releases large amounts of energy when its nuclei split apart. It starts when neutrons are fired at the fuel, causing some of its large, unstable nuclei to split into two smaller nuclei of roughly equal size. |
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What do fuel rods do in nuclear reactors? |
Capture the neutrons, and emit neutrons when nuclei in the rod split. The chain reaction in the reactor has to be controlled or the reactor would overheat. |
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What do control rods do? |
Absorb some of the neutrons and slow down the reaction. They can be moved further into and out of the reactor to absorb more or less neutrons. |
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How is low level radioactive waste dealt with? |
Burying it in secure landfill sites. |
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How is intermediate radioactive waste dealt with? |
Sealed in concrete blocks and then put in steel canisters for storage. |
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How is high level radioactive waste dealt with? |
Sealed in glass and steel, then cooled for about 50 years before its moved to permanent storage. |
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How can ionising radiation damage living cells? |
A high dose tends to kill cells outright, causing radiation sickness. Lower doses tend to damage cells without killing them which can cause cancer. |
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Irradiation |
Being exposed 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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Contamination |
Picking up some radioactive material, e.g. by breathing it in. You'll still be exposed to the radiation once you've left the radioactive area. |
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Who is more at risk of radiation exposure? |
Uranium miners and processors Miners Some medical staff Workers in nuclear power plants Airline staff |
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Where does background radiation come from? |
Natural radioactive elements Space Human activity |
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What is ionising radiation useful for? |
Treating cancer Sterilising medical equipment Sterilising food Detecting diseases using tracers. |
