A salt dissolves in hot water and crystallises again as the solution cools. Read the burette and thermometer diagrams, work out the solubility for each experiment, draw a smooth solubility curve and use it, then evaluate the method. Every attempt uses a different salt sample and different readings. Allow about 25 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.
This workout needs JavaScript.
Every burette reading to 0.1 cm³ from the bottom of the meniscus, each total volume as the reading minus the start reading, every temperature to 0.5 °C, and all values to one decimal place.
Mass of salt × 100 ÷ volume of water, to 3 significant figures, using your own volumes.
A solubility scale that fits the points and uses more than half of the grid, and a smooth curve close to every point from the first to the last.
Values read from your own curve: a solubility, a temperature, and the mass of crystals formed on cooling.
Why extending the curve is risky, a source of error, an improvement and a safety precaution.
The marking follows the conventions in published Cambridge mark schemes. The experiments, readings and wording on this page are our own.