The red hot quarter boils methanol, twice... A Discrepant Event is an event that defies eveything you already know. The explanantion- The intense heating allows the copper to mix with (or float up through) the nickel cladding. The sudden release of bubbles is likely an example of the "Leidenfrost" effect. The alcohol forms a vapour layer around the coin slowing the rate at which heat can escape. When the liquid stops boiling, the insulating vapour layer around the coin collapses and the coin-liquid contact is more efficient at transferring heat away from the metal. This results in a sudden rush of bubbles as the coin cools to below the boiling point of methanol. The collapse of the gas layer also reveals the new colour of the coin. This mimics an exothermic phase transition and is a dramatic way to illustrate how a physical (or chemical) change can result in a sudden release of energy.