Available practice: 73 of 75 marks. Parts 7(a) await marking support. Scores cover available parts only. Theory Paper 2: Section A is compulsory and Section B offers a choice of two questions. Four published mark-scheme discrepancies across the two variants are held from automatic marking.
(a)(i)State what is meant by melting point.
Answer guidance
State A short answer. No explanation is needed, and adding one cannot earn extra marks.
[2 marks]
(a)(ii)For a liquid between its melting and boiling points, describe in molecular terms what changes when the liquid evaporates.
[3 marks]
(b)(i)The boiling point of nitrogen is –196 °C. Liquid nitrogen, below its boiling point, is stored in a vacuum flask, as shown in Fig. 10.1. The flask has two glass walls with a vacuum between them. Suggest where, in the apparatus shown in Fig. 10.1, evaporation occurs.
Answer guidance
Suggest More than one answer may be acceptable, so long as it is consistent with the physics.
[1 mark]
(b)(ii)The boiling point of nitrogen is –196 °C. Liquid nitrogen, below its boiling point, is stored in a vacuum flask, as shown in Fig. 10.1. The flask has two glass walls with a vacuum between them. State and explain the advantage of having a vacuum between the two glass walls.
Answer guidance
State A short answer. No explanation is needed, and adding one cannot earn extra marks.
[3 marks]
(c)(i)The liquid nitrogen reaches –196 °C, its boiling point. A small piece of metal at 20 °C is lowered slowly into the liquid nitrogen. Bubbles form within the liquid nitrogen as it boils. State what is inside the bubbles.
Answer guidance
State A short answer. No explanation is needed, and adding one cannot earn extra marks.
[1 mark]
(c)(ii)1A 50 g metal sample cools from 20 °C to −196 °C in liquid nitrogen. Its specific heat capacity is 0.39 J/(g °C). Calculate the thermal energy lost by the metal.
Answer guidance
Calculate Show your working. The method can earn marks even when the final value is wrong, and a bare answer often cannot.
[3 marks]
(c)(ii)2The 50 g metal sample cools from 20 °C to −196 °C in liquid nitrogen. Its specific heat capacity is 0.39 J/(g °C), and nitrogen’s specific latent heat of vaporisation is 200 J/g. Calculate the mass of nitrogen that boils away.
Answer guidance
Calculate Show your working. The method can earn marks even when the final value is wrong, and a bare answer often cannot.
[2 marks]
5054/21/M/J/16Cambridge O Level Physics 5054 · May/June 2016 · Paper 2 variant 1 · Question 10