Penguins huddle to keep warm, and 0610 Paper 6 tests this with test-tubes of hot water as model animals. Here one tube stands alone while five identical tubes are held together with a rubber band, every tube holding 15 cm³ of water at 70 °C. You read both thermometers every minute for 8 minutes. Watch the set-up built step by step, with the variables and the graph beside it, then build it yourself and check it against the points the examiners look for.
Examiner reports used: 0610 June 2023 (Paper 62), November 2023 (Paper 61) and November 2025 (Paper 63).
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The same size and type of test-tube, the same volume of water in every tube (measured in a measuring cylinder), the same starting temperature, the same bench at the same time. A rubber band on the single tube as well. Only the huddling is different.
One thermometer in tube A and one in the central tube of the huddle. Wait for the reading to stop rising, then read at eye level to the nearest 0.5 °C.
Headings time / min and temperature / °C, starting at 0 minutes, every value to one decimal place. A line graph of both sets with a key, the points covering at least half the grid.
Rate of heat loss = change in temperature ÷ time, in °C per minute, from the starting temperature. Huddling slows heat loss because each tube has less surface exposed.
More set-ups: all IGCSE biology Paper 6 set-up builders. Then practise in the investigations trainer. The experiment, readings and wording on this page are our own.