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GCSE Physics > Topic 6 - Radioactivity > Flashcards

Topic 6 - Radioactivity Flashcards

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1
Q

SP6a - What did the plum pudding model look like?

A

Made of positively charged mass with negatively charged electrons scattered throughout.

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2
Q

SP6a - What was the experiment that Erenest Rutherford conducted and what did he do?

A
  • The gold foil experiment.
  • He fired alpha particles through various substances e.g. thin gold foil.
  • Firing alpha particles from a source and having a detector behind whatever substance he used so that he could find out if the particles pass through.
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3
Q

SP6a - What were the results drawn of the gold foil experiment and what conclusions were drawn from this?

A
  • Most particles passed straight through
  • Some were deflected slightly
  • Others were bounced back
  • This means that most of an atom is empty space.
  • Aditionally, atoms have a concentrated area of positive charge.
  • This is why some were reflected back.
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4
Q

SP6a - What is the radius of a nucleus and the radius of an atom?

A
  • N: 1x10-15
  • A: 1x10-10

(Atom is 10,000 times bigger)

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5
Q

SP6b - What are the charges, locations and relative masses of protons neutrons and electrons?

A

P:

  • Inside nucleus
  • +1 charge
  • mass of 1

N:

  • Inside nucleus,
  • no charge
  • mass of 1

E:

  • Orbiting nucleus
  • -1 charge
  • mass of 1/1835 (negligible)
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6
Q

SP6b - What does the atomic number of an atom represent?

A
  • The number of protons in the nucleus.
  • Different elements have different proton numbers
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7
Q

SP6b - What does the mass number of an atom represent?

A
  • The mass of the atom.
  • Protons plus neutrons.
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8
Q

SP6b - What is an isotope?

A

Two atoms of the same element with different masses (Same atomic number but different mass numbers)

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9
Q

SP6c - What can happen if an atom gains enough energy and what does this create?

A
  • An electron can move to a higher orbit.
  • When it returns back to its orbit it emits energy in the form of visible light.
  • The wavelength (and therefore colour) depends on the change in orbit.
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10
Q

SP6c - What do we use to see the light produced by an atom?

A
  • An emission spectrum.
  • A black line spectrum with coloured lines along it displaying which wavelengths were emitted.
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11
Q

SP6c - How will the emission spectrum of an element relate to its absorption spectrum and what does this tell us?

A
  • The coloured areas on the emission spectrum will be blacked out on the absorption spectrum and vice versa.
  • This means that the wavelengths that are emitted are also the wavelengths that are absorbed.
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12
Q

SP6c - If an atom gains more energy than needed to just move an electron to another orbit, what can happen and what is this called?

A
  • The atom can loose an electron.
  • This is called ionisation as the atom has become an ion
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13
Q

SP6c - What is an ion?

A

An atom that is charged due to a gain or loss of electrons.

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14
Q

SP6c - What do we call radiation that causes an atom to loose an electron?

A

Ionising radiation

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15
Q

SP6d - What is background radiation?

A

Radiation that is constantly all around us at a safe level.

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16
Q

SP6d - What are the six main sources of background radiation

A
  • Medical
  • Ground and buildings
  • Food and drink
  • Radon gas
  • Cosmic rays
  • Nucelar
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17
Q

SP6d - Which source of backgrond radiation accounts for most of it and approximately how much is it?

A

Radon gas just under 50%

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18
Q

SP6d - What are ways of measuring radioactivity?

A
  • With a Geiger
  • Mueller tube / counter Meausres the count rate
  • Photographic film (badges called dosimeters) Gets darker / changes colour as its exposed to more radioactivity
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19
Q

SP6d - Before measuring the radioactivity of a source what must be done?

A

Measure the background radiation so you can take this away from the radiation that you measure or else you value will be the source’s radiation + the background radiation.

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20
Q

SP6e - What is an alpha particle?

A

A helium nucleus consisting of 2 protons and 2 neutrons

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21
Q

SP6e - What is a beta minus particle?

A

An electron

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22
Q

SP6e - What is a beta plus particle?

A

A position (A positive electron)

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23
Q

SP6e - What don’t gamma rays have that other radiation does.

A

Since it is an EM wave and not a particle, it doesn’t have a charge.

24
Q

SP6e - Rank and explain the types of radiation in terms of ionisation.

A
  • Alpha (Most)
  • Beta (+/-)
  • Gamma (Least)

Since alpha particles are emitted at high speeds thay carry most energy and are best at ionistation.

This is the opposite for Gamma.

25
Q

SP6e - Rank the types of radiation in terms of penetration / range.

A
  • Gamma (Most)
  • Beta (+/-)
  • Alpha (Least)
26
Q

SP6e - What does it take to stop each type of radiation?

A
  • Alpha: paper/skin/few cm of air
  • Beta: few m of air/3mm of alluminium
  • Gamma: few Km of air/ few cm of lead/ several m of concrete
27
Q

SP6f - What occurs in alpha decay?

A

An unstable nucleus looses 2 protons and 2 neutrons (an alpha particle) causing its mass number to decrease by 4 and its atomic number to decrease by 2.

28
Q

SP6f - What occurs in beta minus decay?

A

A neutron decays into a proton and a high energy electron.

29
Q

SP6f - What occurs in beta plus decay?

A

A proton decays into a neutron and a high energy positron.

30
Q

SP6f - What occurs in gamma decay?

A

An unstable nucleus emits a gamma ray becoming more stable.

31
Q

SP6g - What is a half-life?

A
  • The time it takes for half the unstable nuclei of a substance to decay
  • The time it takes for the count rate of a radioactive substance to decrease by half.
32
Q

SP6g - If a substance has a half-life of 2 minutes and has a count rate of 128Bq, what will its count rate be after 8 minutes?

A

8/2 = 4

24 = 16

128/16 = 8

8Bq

33
Q

SP6h - How might you use radiation to treat food?

A

Irradiating fresh produce makes it safer to eat and increases its life time.

34
Q

SP6h - How might radioactivity be used in hospitals?

A
  • To detect and treat cancer (radiotherapy and PET scans)
  • To sterelise equipment
35
Q

SP6h - How may radioactivity be used when a pipe leaks?

A
  • A gamma source is added to water and passed through the pipe and a geiger tube is placed on top.
  • Areas with leaks have higher levels of radiation.
36
Q

SP6h - When making paper, how may radioactivity be used?

A
  • A beta source is placed on one side of the paper and a detector on the other.
  • When the detector detects too few beta particles passing through, the paper is too thin and so adjusts the force applied to the paper.
  • When too many pass throught the opposite happens.
37
Q

SP6i - What is it called when the DNA inside a cell is damaged by ionising radiation?

A

Mutation

38
Q

SP6i - Why do mutations in cells have long term effects?

A

Because they can be passed down through generations

39
Q

SP6i - How may someone hande radioactive sources safely?

A
  • Using tongs
  • Not pointing the source at people
  • Storing the source in lead lined containers
40
Q

SP6i - How do medical staff reduce their exposure to radioactive sources?

A
  • Increasing their distance
  • shielding the source
  • Minimising time spent near the source
  • Wearing dosimeter badges to monitor exposure
41
Q

SP6i - What sort of sources are used when treating cancer patients?

A

Ones with short half - lives

42
Q

SP6i - What is the difference between irradiation and contamination?

A

A substance becomes irradiated if exposed to a radioactive source but is contaminated if it is still radioactive even when the source is taken away.

43
Q

SP6i - How may a nuclear accident affect food supply?

A
  • Water and soil nearby gets contaminated which contaminates the crops and plants.
  • Animals that feed on this also become contaminated,
44
Q

SP6j - How may a gamma camera be used in medical diagnosis?

A
  • A radioactive tracer with a short half - life is injected into the blood stream.
  • The gamma camer detects areas of high radiation.
  • This can help in diagnosing internal bleeding.
  • The tracer is made using radioactive glucose molecules because cancer cells take up glucose quickly.
45
Q

SP6j - How does a PET scan work?

A
  • A tracer that has beta plus decay is injected into the patient.
  • When the emitted positron meets an electron, they annihilate each other and release two gamma rays in opposited directions.
  • The PET scnanner moves around the patient detecting where gamma radiation originates from forming a series of images.
46
Q

SP6j - What is internal radiotherapy and what are the pros and cons?

A

A beta emitter is placed next to the tumour inside the body.

47
Q

SP6j - What is external radiotherapy?

A

Several beams of gamma rays, X-rays or protons are fired at the tumour from multiple directions.

48
Q

SP6j - Why is external radiotherapy preffered to internal radiotherapy?

A

Internal radiotherapy can harm can harm healthy cells while external radiotherapy specifically targets the cencer cells. Internal radiotherapy is only used in situations where the benefit greatly exceeds the risk.

49
Q

SP6k - What are the pros and cons of using nuclear energy over fossil fuels to generate energy?

A

Pros:

  • Sources of uranium will take a lng time to expire
  • They store mre energy per kg
  • They cause less deaths
  • The stations themsleves don’t release GH gases

Cons:

  • The extraction process release many GH gases
  • Waste substances can contaminate environment if not stored properly
  • Very expensive to decomission safely
  • Nuclear accidents cause many deatsh and long term effects
50
Q

SP6l - What is nuclear fission?

A

When an unstable nucleus absorbs a neutron, it decays releasing two smaller daughter nuclei, neutrons and energy.

51
Q

SP6l - If the neutrons released by nuclear fission go on to cause another nucleus to decay, what is this called?

A

A chain reaction

52
Q

SP6l - What are the jobs of the moderator and the control rods in a a reactor?

A
  • CR: Rods that contain elements that absorb neutrons. Can be lowered or raised to control how much reation is taking place and how much energy is generated.
  • M: Material which slows down neutrons. This allows the neutrons to be absorbed increasing rate of reaction
53
Q

SP6l - How does the energy generated fin a nuclear reactor get transferred into electrical energy?

A
  • Thermal energy is generated from the reaction process.
  • This is used to heat up a source of water turning it into steam.
  • This steam turns turbines which turn and power the generator generating electricity.
54
Q

SP6m - What is nuclear fusion and where does it take place?

A

Nuclear fusion occurs when two smaller nuclei (typically hydrogen) join together to form a larger atom (helium) and energy in the form of gamma radiation

55
Q

SP6m - What conditions are needed for nuclear fusion to occur and why?

A
  • Nuclear fusion requires that the nuclei are travelling at over 1,000,000 m/s and in temperatures hotter than the sun.
  • This is to overcome the electrostatic repulsion that would otherwise repel the two like charged nuclei away from each other.
56
Q

SP6m - Why aren’t there any working nuclear fusion stations?

A

To maintain conditions required to overcome elctrostatic repulsion is extremely costly and hard to sustain on earth.

GCSE Physics (17 decks)

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