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Q & A: boiled or distilled

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Most recent answer: 07/23/2009
Q:
Is it true that boiled tap water is the same as distilled water?
- Laura (age 50)
Kentucky
A:
Nope. Tap water has dissolved minerals in it. If you boil the water, but obviously not enough to boil it all away, some water will leave as vapor, so the water left will have a higher concentration of minerals than at the start. Distilled water is what you get if you gather that water vapor on some cool surface. It's almost pure water, with the minerals and other impurities left behind.

There are a few purposes for which the boiled and distiiled water are similar. For example, if there is a problem with bacteria in the water, both the boiled and distilled water should be safe to drink, since the heat should kill the bacteria. If the problem is not bacteria but the presence of toxic or otherwise undesirable solutes, then boiling will not help but distilling it will. This is a problem when, say, converting seawater to drinking water -- boiling will not remove the salt but distilling it will.

Mike W. (and Tom)

(published on 10/22/2007)

Follow-Up #1: What is the purpose of boiling distilled water (chemistry wise)?

Q:
What is the purpose of boiling distilled water (chemistry wise)?
- Ella (age 48)
Perth, W-A
A:
The only thing I can think of is that there might be some gases dissolved in the water, like air or carbon dioxide, and boiling it would get rid of a lot of them.

LeeH

-unless maybe you're thinking of the boiling involved in the distillation itself, rather than some boiling afterwards. Boiling water give off fairly pure water vapor, leaving other chemicals behind. The condensed vapor then is the distilled water.  Mike W.

(published on 07/23/2009)

Follow-up on this answer.