What happens when a drop of water falls on a hot chimney?

It evaporates rather quickly. The hotter the chimney the fast it will evaporate. Water dropped on a clean hot flat plate like a frying pan will display the Leidenfrost effect where the water surface close to the pan vapourizes and forms a film that prevents the drop from boiling by insulating it from the heat source. read more

When a drop of water falls on a hot glass chimney there is a sudden drop of temperature on the spot where the water drop hits. This decrease in temperature makes the glass to contract. The stress developed on the site of contraction is responsible for the cracking of the glass chimney. read more