Q: Which one boils faster cold water or warm/hot water? Jennifer Washington, Presque Isle, ME

AskFN: Trick question, right? In spite of whatever rumors may be floating around, you can put your trust in common sense: hot water reaches a boil faster. To understand why, think of temperature not in terms hot/cold but in terms of fast/slow. Temperature is an index of the average speed of molecules within a substance. The faster molecules circulate, the hotter the substance and thus the higher the temperature; the slower, vice versa. Attempting to boil water with cold water versus hot is like the difference between going from zero to 60mph versus going from 45mph to 60 - it's no contest.

So why don't we always cook with hot tap water? What's wrong with saving a little time? The answer can be summed up in a word: lead. Hot water dissolves lead in home plumbing more quickly than cold water, and far and away most of the lead that comes out of our taps comes from our own home plumbing. Whether you live in a very old home with lead pipes or a very new home with copper piping joined with lead-containing solder, hot tap contains more lead than cold. In recognition of this, the EPA advises consumers to always use cold water for cooking. If you've got any worries about lead in your tap water, have your water tested by a state certified lab, and check first with your public water supplier. Some of them will test for free.

Code of Federal Regulations CFR code : 40CFR sec. 141.85 (a) (1) (4B2)
Lead in Drinking Water

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