Timing a reaction at different temperatures is a favourite Question 1 in 0620 Paper 5, and Paper 6 asks the same experiment from diagrams. By hand, measure the sodium thiosulfate and the acid in measuring cylinders, warm the thiosulfate in a water bath with hot water from the kettle, stand the beaker on the printed cross and add the acid. You decide when the cross has gone, then read the stopwatch and the thermometer. Plot your own graph with a smooth curve, read a time from it and explain the trend. Every attempt uses a different rate. Allow about 35 minutes.
Checked: Cambridge IGCSE Chemistry 0620 Papers 5 and 6, 2020 to 2025. 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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Headings with units, temperatures to the nearest 0.5 °C and times in whole seconds, Experiment 1 at room temperature and four warmer mixtures at least 5 °C apart (none above 55 °C), readings that match your thermometer and stopwatch, the same volumes every time, and an accuracy mark for timing the real end point.
A sensible linear scale for time, every point plotted within half a small square, and a smooth curve of best fit through your points.
The experiment with the fastest rate (the shortest time), and a time read from your own curve.
The trend and its explanation in terms of particles and collisions, why the volumes stay the same, how to keep the temperature constant, a light sensor for the end point, and a safety precaution with its reason.
The marking follows the conventions in published Cambridge mark schemes. The experiments, readings and wording on this page are our own.