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Edexcel GCSE Physics > Topic 6: Radioactivity > Flashcards

Topic 6: Radioactivity Flashcards

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1
Q

State the sub-atomic particles in the atom, their charge and location.

A
  • Positively charged protons in the nucleus
  • Neutrally charged neutrons in the nucleus
  • Negatively charged electrons that orbit the nucleus in shells (rings) in different fixed distances
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2
Q

Describe the size and mass of the nucleus in relation to the rest of the atom.

A
  • Radius of nucleus is a lot smaller than radius of atomic
  • Most of an atom’s mass is concentrated in the nucleus
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3
Q

State the relative mass and charge of the sub-atomic particles:
1. Proton
2. Neutron
3. Electron
4. Positron

A
  1. 1, +1
  2. 1, 0
  3. 0.0005, -1
  4. 0.0005, +1
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4
Q

State the size of an atom.

A

~0.1 nanometres

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5
Q

What is an isotope?

A
  • atoms of the same element with the same number of protons but a different number of neutrons
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6
Q

What occurs when electrons change orbit (move closer or further to the nucleus), in terms of electromagnetic radiation?

A
  • When electrons move to a higher orbit (move further away from the nucleus), the atom has absorbed electromagnetic radiation.
  • When electrons fall to a lower orbit (move closer to the nucleus), the atom has emitted electromagnetic radiation.
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7
Q

What is required for an electron leave an atom?

A
  • enough energy
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8
Q

State the types of decay (5).

A
  • Alpha
  • Beta Minus
  • Beta Plus
  • Gamma
  • Neutrons
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9
Q

Describe alpha decay.

A
  • a helium nucleus
  • highly ionising
  • weakly penetrating
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10
Q

Describe beta minus decay.

A
  • electron
  • medium ionising
  • medium penetrating
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11
Q

Describe beta plus decay.

A
  • positron
  • medium ionising
  • medium penetrating
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12
Q

Describe gamma decay.

A
  • radiation
  • low ionising
  • highly penetrating
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13
Q

What is background radiation?

A
  • weak radiation that can be detected from natural or external sources
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14
Q

Give examples of background radiation.

A
  • cosmic rays
  • radiation from underground rocks
  • nuclear fallout
  • medical rays
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15
Q

What are two methods of measuring radioactivity?

A
  • photographic film
  • Geiger-Muller Tube
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16
Q

Describe the purpose and use of photographic film when measuring radioactivity (2).

A
  • the initially white film becomes darker when it absorbs radiation
  • worn as bandages by people who work with radiation to check how much exposure they have had
17
Q

Describe the purpose and use of the Geiger-Muller Tube when measuring radioactivity (3).

A
  • it is a tube that detects radiation
  • each time it absorb radiation it sends and electrical pulse to the machine which produces a clicking sound
  • the greater the frequency of clicking sounds, the more radiation present
18
Q

How did the atomic model change over time? (4)

A
  • Dalton - Everything was made up of atoms
  • JJ Thompson - Discovered the electron (plum pudding model)
  • Rutherford - Discovered most of the atom’s mass is located in the nucleus (good foil experiment)
  • Bohr - Discovered that electrons orbit the nucleus in fixed rings
19
Q

Describe (radio) activity? (2)

A
  • number of decays in a sample per second
  • measured in Bequerel, Bq
20
Q

What is the relationship between atom concentration in a sample and the chance that the atoms will decay?

A
  • the greater the concentration of atoms in a sample, the more likely at least one of them will decay
21
Q

What is the half-life of an isotope?

A
  • the time taken for half the nuclei in a sample to decay
22
Q

What is the formula for net decline?

A

net decline = (initial number - number of X half lives) / (initial number)

23
Q

State uses of radioactivity. (3)

A
  • smoke alarms
  • irradiation of food
  • diagnosis and treatment of cancer
24
Q

How is radioactivity used in smoke alarms?

A
  • americium emits alpha particles that are stopped in air as it is weakly penetrating
  • alpha particles ionise air particles and makes them charged, making a current
  • if smoke enters the air around the smoke alarm, the current drops in the circuit
  • causing the alarm to sound
25
Q

How is radioactivity use to irradiate food?

A
  • gamma rays transfer to bacteria killing them and sterilising food
  • also used to delay ripening of fruit
26
Q

How is radioactivity used to diagnose and treat cancer? (4)

A
  • patient consumes or is injected with gamma emmiter
  • while passing though the body, an external detector can picture where the tracer has collected in the body, which can reveal tumours
  • gamma rays are used on the tumour, killing the cancer cells
  • however, exposing rays on healthy cells can cause them to mutate
27
Q

What are the dangers of ionising radiation, in relation to short and long half-lives? (4)

A

short half- life
- the source presents less risk, as it does not remain strongly radioactive, and quickly dies down
- presents less of a long term risk

long half-life
- the source remains weakly radioactive for a long period of time
- americium used in smoke alarms as it does not need to be frequently replenished and is weak so it will not harm anyone

28
Q

What are some safety measures when using radioactivity? (2)

A
  • use tracers with short half-life
  • leave room during radioactive tests as their health will be at risk in the long term
29
Q

State the the two different types of radiation?

A
  • Contamination
  • Irradiation
30
Q

Describe contamination in terms if radiation? (2)

A
  • last for a long period of time
  • the source of the radiation is transferred to an object (e.g skin)
31
Q

Describe irradiation in terms of radiation? (2)

A
  • lasts for only a short period of time
  • the source emits radiation, which reaches the objects (e.g used medically to kill bacteria)
32
Q

Describe thoroughly how cancer is treated using radioactivity. (4)

A
  • a beam of gamma radiation rotates around the body
  • focuses on tumour and momentarily passes across healthy cells to ensure minimal damage occurs
  • takes a long time to fully treat and greater risk of long-term side effects
  • a needle which holds radioactive material that directly injects into tumour can also be used
33
Q

Describe how PET scanners are used in relation to radioactivity? (4)

A
  • radioactive tracer made locally as it has a short half-life and cannot be stored for a long time
  • radioactive tracer is inserted into body and is tagged onto desired chemical and travels with it
  • scanner records where the tracer emits radioactivity which creates a live 3D visualisation of the body
  • used to show effectiveness of treatment or diagnose cancer, epilepsy or Alzheimer’s
34
Q

How is nuclear power generated?

A

fission chain reaction - uranium fuel splits releasing neutrons, which are absorbed by further uranium nuclei which split and release two daughter nuclei and two more neutrons, releasing energy

35
Q

What are the advantages and disadvantages of nuclear power?

A

Advantages
- no carbon dioxide produced

Disadvantages
- radiation leaking
- stigma around nuclear power by public
- waste disposal is difficult - must be stored deep underground

36
Q

What are nuclear fusion reactions?

A
  • small nuclei forced together under immense pressure and heat to form a heavier nucleus, releasing energy
  • energy source of stars
  • electrostatic repulsion between protons means that a lot of energy is required to bring both nuclei close enough to fuse
  • expensive and impractical to do on an industrial scale
37
Q

What is radioactive decay?

A
  • when an unstable nucleus decays into two smaller nuclei, releasing energy
38
Q

How can a chain reaction be controlled in an industrial setting? (3)

A

Moderators
- water or graphite
- slows down emitted neutrons to be absorbed to further fissions

Control rods
- these are boron rods in the reactor core, which absorbs excess neutrons, preventing a chain reaction

Water coolant
- heat energy from chain reaction is absorbed by water (coolant)
- water then evaporates into steam and powers the turbine to produce electricity from generator

Edexcel GCSE Physics (1 decks)

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