Physics · Oct / Nov 2020 · Paper 42 · Question 5
0625
As printed in the paper
Show the answer and mark scheme
5(a)(i)[2]
(thermal) energy (needed) to change state
of unit mass / 1 kg (of material) NOT per °C
5(a)(ii)[2]
molecules must be separated OR (intermolecular) bonds must be broken / overcome
work done (against bonds) OR energy is required / needed
NOT increase of KE / speed
5(b)[3]
E = ml in any form or (l =) E ÷ m
words, symbols or numbers
(m =) 1.5 OR 1500 OR OR 3.8 – 2.3
OR 3800 – 2300
(l = 1.26 × 106 ÷ 1.5 =) 8.4 × 105 J / kg
5(c)[2]
insulate OR apply lagging / insulation (to container)
reduction of thermal energy / heat losses
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