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Paper 6 style practice paper: Alternative to practical — mark scheme

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QQ/IGCSE-PHYS/P6S

IGCSE · Cambridge IGCSE Physics (Extended)

Mark scheme

Alternative to practical

Paper 6 style practice paper · Maximum mark: 40

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: Practical measurements[20 marks]

QuestionAnswer and marking pointsMarks
1(a)

Average = (2.50 + 2.52 + 2.48) ÷ 3 = 2.50 cm. Repeating reduces the effect of small reading errors and random variation.

  • 2.50 cm [1]
  • repeats average out random errors [1]
2
1(b)

V = π × 2.50² × 5.00 ÷ 4 = π × 6.25 × 5.00 ÷ 4 = 24.5 cm³.

  • correct formula used with average diameter [1]
  • d² × L evaluated [1]
  • 24.5 cm³ [1]
3
1(c)

ρ = 178.0 ÷ 24.5 = 7.3 g/cm³. [1]

1
Total for Question 16
2(a)

The ammeter is in series, so the lamp’s current passes through it; the voltmeter is in parallel across the lamp, so it compares the p.d. at its two terminals.

  • ammeter in series [1]
  • voltmeter in parallel across the lamp [1]
2
2(b)

R = V/I = 2.0 ÷ 0.40 = 5.0 Ω.

  • use of R = V/I [1]
  • 5.0 Ω [1]
2
2(c)

The resistance increases: the hot filament’s ions vibrate more and impede the electrons. On the graph of I against V the points curve — the current gains less than proportionally as V rises.

  • resistance increases [1]
  • filament heats, impeding electrons [1]
  • I–V points curve / not proportional [1]
3
Total for Question 27
3(a)

From about 60 s to about 120 s: the temperature stays constant at 48 °C, the melting point, while the change of state happens.

  • between about 60 s and 120 s [1]
  • constant temperature at the melting point [1]
2
3(b)

Before the plateau the temperature falls 6 °C per 30 s; after it, about 4 °C then 4 °C per 30 s — so the block cools faster before melting than after.

  • pre-plateau gradient quoted [1]
  • comparison stated correctly [1]
2
3(c)

Any sensible improvement with reasoning: take readings every 10–15 s near 48 °C to pinpoint the plateau; insulate the block lightly so it cools more slowly and the plateau lasts longer; use a data-logger for continuous readings.

  • valid improvement named [1]
  • linked to showing the plateau better [1]
  • third mark for a reasoned second suggestion or detail [1]
3
Total for Question 37

Section B: Planning, observations and analysis[20 marks]

QuestionAnswer and marking pointsMarks
4(a)

Clamp the spring vertically with the rule fixed beside it; record the unstretched length; add the weight, wait for the spring to stop moving, then read the new length at eye level to avoid parallax; subtract to find the extension.

  • measure unstretched length first [1]
  • read at eye level to avoid parallax [1]
  • extension = new length − original length / wait until still [1]
3
4(b)

The points lie on a straight line through the origin: the extension is proportional to the load on the straight part of the spring’s behaviour.

  • axes labelled with units [1]
  • points plotted correctly [1]
  • straight line through origin: proportionality stated [1]
3
4(c)

17.5 mm (read or interpolated from the straight line: 3.5 × 5.0 mm/N). [1]

1
Total for Question 47
5(a)

v = d/t = 102 ÷ 0.30 = 340 m/s.

  • use of v = d/t [1]
  • 340 m/s [1]
2
5(b)

Small timing and setup variations are random; averaging them out gives a value closer to the true speed and reduces the effect of any single poor measurement.

  • variations are random [1]
  • averaging reduces their effect [1]
2
5(c)

Any sensible improvement with a reason: increase the microphone separation so the time is larger and the fractional timing error smaller; use a sharper sound (clapper board or electronic pulse) so start and stop are precise; check the microphones are exactly 102 m apart with a tape.

  • valid improvement [1]
  • reason linked to accuracy [1]
2
Total for Question 56
6(a)

Each nucleus has an equal, fixed chance of decaying in a given time interval, like each die having an equal chance of showing a six; the decays happen randomly and independently, and decayed nuclei are gone for good.

  • equal fixed probability per interval [1]
  • random and irreversible removal [1]
2
6(b)

About 32 remain after roll one and about 16 after roll two; in the real process the count rate (activity) of the sample halves.

  • 32 then 16 predicted [1]
  • activity / count rate named as the halving quantity [1]
2
6(c)

No — decay is random, so individual results scatter around the expected value; 34 out of 64 is close to the expected half, and a large number of trials would average near 32.

  • random variation expected [1]
  • close to half / averaging over trials [1]
2
6(d)

Any valid limitation: real nuclei decay continuously rather than in discrete rolls; real half-lives are usually much longer; dice are removed in whole numbers while decay is a continuous process.

  • valid limitation [1]
1
Total for Question 67

— End of mark scheme —