Collecting hydrogen from magnesium and dilute acid and reading the volume every 30 seconds is one of the most common IGCSE Chemistry Paper 5 and Paper 6 experiments. By hand, set the measuring cylinder upside down in the trough, pour 50 cm³ of acid into the flask, drop in the magnesium and get the bung back in before the gas escapes, then read the upside-down scale each time the stopwatch pauses. Do it with two acids, plot both curves, label them and explain what they show. Every attempt uses different acids. 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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A heading with its unit for each volume column, all eight volumes for each experiment read from your own measuring cylinder to the nearest 1 cm³, and a mark for using 50 cm³ of acid each time and losing little hydrogen, so that both final volumes come close to what the magnesium can make.
A linear y-axis scale that uses more than half of the grid, every point within half a small square, two smooth curves starting at (0,0), each line labelled, and two volumes read from your curve with the volume between them in cm³.
The steeper line shows the more concentrated acid; more acid particles in the same volume give more collisions per second; the same mass of magnesium with excess acid gives the same final volume; and a sketch of the line for a new condition.
Gas escaping before the bung is replaced, an improvement that starts the reaction only once the flask is sealed, and the effect of the temperature rise with a water bath to control it.
The marking follows the conventions in published Cambridge mark schemes. The experiments, readings and wording on this page are our own.