A-LevelPhysicsThermodynamics9702/42 · Oct/Nov 2019 · Q211 Marks

what is seen through the microscope

(a)(i)what is seen through the microscope[1]
(a)(ii)how Brownian motion provides evidence for the nature of the movement of gas molecules.[2]
(b)(i)the amount, in mol, of the gas amount = ..................................................... mol [3][3]
(b)(ii)the thermal energy transfer during the change. energy transfer = ..................................................... J [2][2]
(c)(i)the quantity of external work done on the gas work done = ..................................................... J [1][1]
(c)(ii)the change in internal energy, with the direction of this change. change = ..................................................... J direction ..................................................... [2][2]

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Mark scheme

Marking points from the official mark scheme (Oct/Nov 2019). The mark or mark type is shown in brackets.

[B1] specks of light moving haphazardly
[M1] (gas) molecules collide with (smoke) particles / random motion of the (gas) molecules
[A1] causes the (haphazard) motion of the smoke particles / causes the smoke particles to change direction
[C1] pV = nRT
[C1] n = (3.51 × 10⁵ × 2.40 × 10⁻³) / (8.31 × 290) or n = (3.75 × 10⁵ × 2.40 × 10⁻³) / (8.31 × 310) or pV = NkT (C1) n = (3.51 × 10⁵ × 2.40 × 10⁻³) / (1.38 × 10⁻²³ × 6.02 × 10²³ × 290) or n = (3.75 × 10⁵ × 2.40 × 10⁻³) / (1.38 × 10⁻²³ × 6.02 × 10²³ × 310)
[A1] n = 0.350 mol or 0.349 mol
[C1] energy transfer = (0.349 or 0.35) × 12.5 × (310 – 290)
[A1] = 87.3 J or 87.5 J
[A1] zero
[A1] 87.3 J or 87.5 J
[B1] increase

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