Thermochemistry is a favourite in 9701 Paper 3: a cup, a thermometer, a stopwatch and a graph you have to extrapolate. By hand, pour the copper(II) sulfate, weigh the zinc, tip it in on time and stir with the thermometer. Then plot your own readings, draw two lines, find ΔT and work through to ΔH. Every attempt uses a different concentration. Allow about 40 minutes.
Checked: Cambridge 9701 Paper 3, February/March 2023 to May/June 2026. Only the papers in our collection are listed, so the real number may be higher. Question papers are available from Cambridge.
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Balance readings exactly as shown (2 decimal places), the mass added by difference, the volume from the cylinder, headings with units, and every temperature to the nearest 0.5 °C with no reading at the moment of mixing.
A line through the steady readings before mixing, a best-fit line through the cooling points after the maximum, both extended to 3.0 min, and ΔT read from the gap between them.
q = m c ΔT with the mass of the solution, moles of the limiting reagent, a check that zinc is in excess, then ΔH with a negative sign and 3 significant figures.
The percentage error in ΔT from two readings, why extrapolation is needed, why the zinc is a powder, and an improvement that really reduces heat loss.
The marking follows the conventions in published Cambridge mark schemes. The experiments, readings and wording on this page are our own.