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Topic 12 Practice Paper: Nuclear physics — mark scheme

QuizQuipPractice Series
QQ/IGCSE-PHYS/T12

IGCSE · Cambridge IGCSE Physics (Extended (Core + Supplement))

Mark scheme

Nuclear physics

Topic 12 Practice Paper · Maximum mark: 30

Notes for markers

  • Award one mark for each point marked [1], up to the marks shown for the part.
  • Accept answers worded differently that show the same understanding.
  • Units are required where the answer line shows one. ecf: allow an error carried forward.

Section A: Multiple-choice questions[10 marks]

QuestionAnswer and marking pointsMarks
Total for Question 11
Total for Question 21
Total for Question 31
Total for Question 41
Total for Question 51
Total for Question 61
Total for Question 71
Total for Question 81
Total for Question 91
Total for Question 101

Section B: Structured questions[20 marks]

QuestionAnswer and marking pointsMarks
11(a)

The atom is mostly empty space. [1]

1
11(b)

There is a very small, positively charged region: the alphas were repelled by its positive charge.

  • very small nucleus / concentrated charge [1]
  • positively charged, repelling the positive alphas [1]
2
11(c)

The nucleus contains most of the atom’s mass — an alpha bouncing back has struck something far more massive than itself.

  • nucleus holds most of the mass [1]
1
11(d)

Charge +2; it is a helium nucleus of two protons and two neutrons.

  • charge +2 [1]
  • two protons and two neutrons [1]
2
Total for Question 116
12(a)

²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂He.

  • daughter ²³⁴₉₀Th [1]
  • alpha as ⁴₂He with equation balanced [1]
2
12(b)

²³⁴₉₀Th → ²³⁴₉₁Pa + ⁰₋₁e.

  • daughter ²³⁴₉₁Pa [1]
  • beta as ⁰₋₁e, balanced [1]
2
12(c)

A neutron in the thorium nucleus changed into a proton plus an electron; the electron was emitted as the beta particle, raising the proton number by one.

  • neutron → proton + electron [1]
  • explains Z rising by one [1]
2
Total for Question 126
13(a)

1320 − 40 = 1280 counts/min. [1]

1
13(b)

60 min = 3 half-lives: 1280 → 640 → 320 → 160 counts/min.

  • three half-lives [1]
  • 160 counts/min [1]
2
13(c)

160 + 40 = 200 counts/min — the background must be added back.

  • background added [1]
  • 200 counts/min [1]
2
Total for Question 135
14(a)

Any two of: cell death, mutations, cancer.

  • two valid effects [1]
1
14(b)

Handle with long tongs at arm’s length; keep the source pointed away from people and work quickly to limit exposure time; store it in a lead-lined box when not in use.

  • tongs/distance and time kept short [1]
  • lead-lined storage / shielding [1]
2
Total for Question 143

— End of mark scheme —