Chemistry · May / June 2025 · Paper 62 · Question 2
0620
As printed in the paper
The question as text
A student investigates the temperature change when anhydrous lithium chloride dissolves in water. The student does five experiments. Experiment 1 • Use a 50 cm3 measuring cylinder to pour 40 cm3 of distilled water into a 100 cm3 beaker. • Use a thermometer to measure the initial temperature of the water. • Add a 2.0 g sample of anhydrous lithium chloride to the water in the beaker. • Continually stir the mixture in the beaker using the thermometer. • Measure the highest temperature reached by the mixture in the beaker. • Empty the beaker and rinse the beaker with distilled water. Experiment 2 • Repeat Experiment 1 using 30 cm3 of distilled water instead of 40 cm3. Experiment 3 • Repeat Experiment 1 using 25 cm3 of distilled water instead of 40 cm3. Experiment 4 • Repeat Experiment 1 using 20 cm3 of distilled water instead of 40 cm3. Experiment 5 • Repeat Experiment 1 using 15 cm3 of distilled water instead of 40 cm3.
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2(a)[4]
all experiments have a mass of 2.0 g of lithium chloride
all temperatures and temperature changes recorded to 1 dp
all five highest temperatures recorded correctly (27.0, 29.0, 30.5, 32.5, 35.5)
all temperature changes calculated correctly (4.5, 6.5, 8.0, 10.5, 13.5)
2(b)[4]
y-axis scale is linear and points extend over halfway up scale
all points plotted correctly
best fit line
2(c)[3]
extrapolation shown on graph, this must be a smooth continuation of line to at least a volume of 45
correct reading from their extrapolation at 45
°C
2(d)[1]
850.5 OR 851
2(e)[2]
(temperature change approximately) doubled / 9 °C
twice as much lithium chloride dissolved / used (so twice as much energy given out)
2(f)[2]
polystyrene is a better insulator than glass / it is an insulator
less heat loss (to the surroundings)
2(g)(i)[1]
(burette more) accurate (than measuring cylinder)
2(g)(ii)[1]
water-bath would keep temperature constant
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