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Paper Kettle
AKA: Boiling Water in a Paper Cup

Summary

Water in a paper cup boils when heated from below with a candle. The cup does not burn.

Operation

This is a fun demonstration that may be conducted as part of a lesson in heat transfer / kindling points or as an end of term fun filler.

A paper cup is filled with approx 100ml of water and suspended using string from a retort stand. A small tea-light type candle is placed beneath the base of the cup and lit. The water should heat up and eventually boil but the cup will not burn and should remain intact.

Waxed cups should not be used for this demonstration as they may catch fire. Students may think that the heat from the candle will burn the cup but the water draws the heat away from the paper, keeping the temperature below the kindling point of the paper cup.

Equipment typically required (per demo):

Four holes are usually made in the top of the cup just below the rim and string is threaded through. The cup is suspended by the string so ensure all lengths are equal and the cup is stable. The cup should be suspended close to the top of the candle to reduce spillage if the cup does burn.

Typical technician preparation time: 10-15 mins.


Safety

Caution

Be aware that if the cup does burn or break, boiling water may leak from it.

The contents of this page are for information only. Please refer to CLEAPSS, SSERC or ASE safety advice and/or publications before undertaking any preparation, practical experiment or using any equipment featured on this site or any other.