Same beaker, same water, same start. Change only the lid.
Cooling of hot water is the most common experiment in IGCSE Physics Paper 6. Here two identical beakers of hot water cool side by side, one open and one with a lid, and you read both thermometers every 30 s. Watch the set-up built step by step, with the variables and the cooling curves beside it, then build it yourself and check it against the points the examiners look for.
Past-paper referenceOriginal experiment, wording and figures, written in the style of Cambridge IGCSE Physics 0625 Paper 6 (Alternative to Practical). It is not copied from a past paper. The “what the examiners said” notes are our paraphrase of the Principal Examiner Reports for Teachers.
Practise next: 0625/63 October/November 2024, (cooling of water in beakers of different sizes) · official past papers
Practise next: 0625/62 February/March 2025, (cooling of an insulated and an uninsulated beaker) · official past papers
Practise next: 0625/62 May/June 2023, (cooling of hot water in a beaker with a lid) · official past papers
Examiner reports used: 0625 March 2023, June 2023 (Papers 61 and 62), November 2023 (Papers 62 and 63), June 2024 (Paper 63), November 2024 (Papers 61 and 63), March 2025, June 2025 (Papers 61 and 63) and November 2025 (Paper 62).
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What a full-mark diagram shows
A fair comparison
Two identical beakers, the same volume of water measured in a measuring cylinder, the same starting temperature and the same room. Only the lid is different.
Accurate temperatures
A thermometer in each beaker with the bulb in the water, not touching the glass. Stir, then read the scale with your eye level with the liquid.
Readings at the right time
Start the stopwatch at t = 0 and read every 30 s, with the stopwatch next to the thermometers or a partner calling the time.
Table, graph and conclusion
Headings t / s and θ / °C, starting at t = 0. A smooth cooling curve on a scale that fills the grid. A conclusion backed by temperature changes quoted from the table.
Habits the examiner reports keep asking for
Units are s and °C, never sec, C or C°. The first time in the table is 0, not 30.
Read the question you are given. “A technique for an accurate reading” means eye level or stirring, not “repeat and average”.
Name the control variable in full: the starting temperature of the water, the volume of water, the room temperature.
Quote values to justify a conclusion: the temperature fall of each beaker over the same time, and the rate in °C/s.
Read a measuring cylinder at the bottom of the meniscus, at eye level, with the cylinder on a level bench.