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This article is on International Young Physicist’s Tournament (IYPT) 2018 (see http://iypt.org/Home) problem number three, Dancing Coin. The task statement as issued by the IYPT-commission reads as follows: Take a strongly cooled bottle and put a coin on its neck. Over time you will hear a noise and see movements of the coin. Explain this phenomenon and investigate how the relevant parameters affect the dance. A theoretical model is presented by which the heat flows into the system can be modelled in order to predict the change in pressure in the bottle. This allows to predict the most important entity involved in the phenomenon, namely the critical pressure at which a lift-off can occur, as well as other dynamic processes involved. In a next step, a possible explanation for the occurrence of the sound is given. Finally, the model quality is evaluated in the light of measured data.

The determining parameter when considering the movement of the coin that has been found during research is coin mass as it affects the pressure dynamics of the system the most. The sound phenomenon, on the other hand, can not be explained to full satisfaction as a result of the resonance of the bottle and the damping of natural frequencies of the coin.