Which boils faster, hot water or cold water?

Dear Cecil:

Which boils faster — hot (or very hot) water or cold water?

P.S.: You must have seen this one coming!

Cecil replies:

I resigned myself to it long ago, buttercup. As any sane and decent person would expect, hot water out of the tap will boil faster than cold water out of the tap. However, water that has been boiled once and allowed to cool will boil faster than hot water out of the tap. That’s because boiling gets rid of the dissolved oxygen usually found in water, making it easier for the water to boil the second time around. There’s money in this somewhere, I’m sure of it.

Send questions to Cecil via cecil@straightdope.com.

Comment on this Column