Answer:
Explanation:
Q1.
(a) 46 200
accept 46 000
allow 1 mark for correct substitution
ie 0.5 × 4200 × 22 provided no subsequent step
2
(b) Energy is used to heat the kettle.
[3]
Q2.
(a) (approximate same size particles as each other and as liquid and gas) touching
do not accept particles that overlap
regular arrangement (filling the square)
(b) condensing
(c) solid
(d) physical
(e) particles have more kinetic energy
particles move faster
(f) mass of the liquid
specific latent heat of evaporation
(g) 2 × 4 200 × 801
672 000 (J)
an answer of 672 000 (J) scores 2 marks
[11]
Q3.
(a) x-axis labelled and suitable scale
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points plotted correctly
allow 5 correctly plotted for 2 marks, 3−4
correctly plotted for 1 mark
allow ± ½ square
2
line of best fit
(b)
allow ecf from line of best fit in part (a)
0.075 (°C/s)
an answer of 0.075 (°C/s) scores 2 marks
(c) Δθ = 11.5 (°C)
a calculation using an incorrect temperature
scores max 3 marks
ΔE = 1.50 × 900 × 11.5
ΔE = 15 525 (J)
ΔE = 15.525 (kJ)
an answer of 15.525 (kJ) or 15.53 (kJ) or 15.5
(kJ) scores 4 marks
an answer of 15 525 (kJ) scores 3 marks
[10]
Q4.
(a) 80 °C
ΔE = 0.5 × 3400 × 80
ΔE = 136 000 (J)
an answer of 136 000 (J) scores 3 marks
(b) energy is dissipated into the surroundings
allow any correct description of wasted energy
(c) put a lid on the pan
allow any sensible practical suggestion
eg add salt to the water
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(d) efficiency = 300/500
efficiency = 0.6
an answer of 0.6 or 60% scores 2 marks
allow efficiency = 60%
an answer of 0.6 with a unit scores 1 mark
an answer of 60 without a unit scores 1 mark
is the conjugate acid
, its conjugate base.
is the conjugate base of
, its conjugate acid.