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Edexcel GCSE Physics (9-1) > SP6 - Radioactivity ✓ > Flashcards

SP6 - 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 is the radius of a nucleus and the radius of an atom?

A
  • N: 1x10-15
  • A: 1x10-10

(Atom is 100,000 times bigger)

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3
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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4
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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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 total number of protons and neutrons in the nucleus of the atom
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8
Q

SP6b - What is an isotope?

A
  • Atoms of the same element that have the same number of protons but different number of neutrons
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9
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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10
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 lose an electron.
  • This is called ionisation as the atom has become an ion
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11
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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12
Q

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

A

Ionising radiation

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13
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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14
Q

SP6c - What is an ion?

A

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

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15
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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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 - 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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18
Q

SP6d - What is background radiation?

A

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

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19
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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20
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.

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21
Q

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

A
  • Gamma (Most)
  • Beta (+/-)
  • Alpha (Least)
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22
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
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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.

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24
Q

SP6e - What is a beta minus particle?

A

An electron

25
Q

SP6e - What is a beta plus particle?

A

A positron (A positive electron)

26
Q

SP6e - What is an alpha particle?

A

A helium nucleus consisting of 2 protons and 2 neutrons

27
Q

SP6f - What occurs in alpha decay?

A
  • An unstable nucleus looes 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 - 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

32
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.
33
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.
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 might you use radiation to treat food?

A

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

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 many beta particles passing through, the paper is too thin and so reduces the force applied to the paper, increasing thickness
  • Whereas, if the paper is too thick, the opposite happens.
37
Q

SP6i - What are the 4 ways medical staff reduce their exposure to radioactive sources?

A
  • Increasing their distance from the source
  • Shielding the source
  • Minimising time spent near the source
  • Wearing dosimeter badges to monitor exposure
38
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,
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 - What is it called when the DNA inside a cell is damaged by ionising radiation?

A

Mutation

41
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.

42
Q

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

A

Ones with short half - lives

43
Q

SP6i - Why are medical radioactive sources made on site?

A

They have a short half life to reduce the time the patient is exposed to the radiation

44
Q

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

A

Because they can be passed down through generations

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 scanner moves around the patient detecting where gamma radiation originates from forming a series of images.
46
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.
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 - What is internal radiotherapy?

A

This is when a beta emitter is placed inside the body, within or very close to the tumour.

49
Q

SP6j - Why is internal radiotherapy more advantageous?

A
  • It is targetted at the tumor, meaning healthy cells are mostly left unharmed
50
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 long time to expire
  • They store more energy per kg
  • They cause less deaths
  • The stations themselves 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 deaths and long term effects
51
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.
52
Q

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

If this isn’t controlled, what can this lead to?

A

A chain reaction

A nuclear explosion

53
Q

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

A
  • Control Rods: They absorb neutrons to control the fission chain reaction.

If the temperature is too high, we lower the control rod so it can absorb more neutrons and reduce fission reaction.

If the temperature is too low, we raise the control rods so it can absorb less neutrons and increase the fission rate.

  • Moderators: Material which slows down neutrons. This allows the neutrons to be absorbed by the fuel easily.
54
Q

SP6l - What is nuclear fission?

A

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

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 - 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

57
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.

58
Q

SPl - What are fuel rods?

A
  • Fuel rods contain uranium and undergo fission so thermal energy is released
59
Q

SP6l / SP6m

Compare and Contrast Nuclear Fission and Fusion

A

Similarities

  • Fission and Fusion both release large amounts of energy during the reaction
  • Differences
  • Fission is the splitting of a nuclei into 2 daughter nuclei whereas fusion is the joining of smaller nuclei to form a larger nuclei.
  • Fission can cause chain reactions and are used in power stations whereas the conditions required for fusion to occur are near impossible to produce in a power station.

Edexcel GCSE Physics (9-1) (17 decks)

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