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Coloma's avatar

How do you boil water?

Asked by Coloma (40313 points ) February 6th, 2013

What’s wrong with bringing hot water to a boil instead of cold?
Clearly it is faster and more efficient. Why don’t we boil hot water more often?

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24 Answers

WestRiverrat's avatar

Actually according to the experiments we did in Junior High school, the cold water absorbs more heat and thys boils faster than the already hot water. I can’t remember why it does, but I remember it does.

Coloma's avatar

Really? That is cool to know!
Well… Coloma fails basic science. lol

jerv's avatar

Rate of heat transfer is proportional to the difference in temperature.

filmfann's avatar

I think @WestRiverrat has that backwards. Hot water freezes faster than luke warm water, but hot water boils faster.

gailcalled's avatar

Here where there is more calcium in hot water (leached out of the pipes, I am guessing, but could be wrong), I always start with cold water. The difference in boiling time is negligible.

Pandora's avatar

I heard that the water in your hot water heater can have more sediments,chemicals and things in it than cold water because it sits and collects in your water tank. That is why people should drain their water tank yearly. The cold water automatically flushes the pipes and any sitting sediment.
So basically, it is just cleaner.
It also depends on what you are cooking. Some things need to heat up with the water while it is heating up.
Eggs for instance. You wouldn’t want to throw a cold egg in hot water to boil.

Coloma's avatar

@Pandora Right, no cold eggs in boiling water, I just got to thinking about this when I went to boil some pasta earlier. Now that you mention it I think I have heard the hot water tank sediment thing somewhere. Wow..I don’t think I’ve ever flushed my hot water tank. lol note to self to check into this

All very interesting. ;-)

gailcalled's avatar

@Pandora: That makes sense. However, I have lived with my water tank, undrained, for 26 years. My plumber, also around for 26 years, has never suggested it.

Coloma's avatar

@gailcalled Yay….you mean I can stop worrying that I am poisoning myself now? haha

Pandora's avatar

@gailcalled and @Coloma I didn’t and my first water tank broke because of all the sediment that had build. It really depends on how clean is the water you get. When I bought my second tank, I drained it after 2 years of use and couldn’t believe the crap that came out. The first tank was really nasty. We had to drain it before removing it. It had nasty sludge.
If you look at your hot water heaters they should have a small outlet to place a pipe or fit a hose to drain it out.
Unless its a tankless water heater. I don’t think those would have any.
Just found this site on how to drain your water heater and why .

josie's avatar

Why does it make any difference. If you use hot water, you will just have to heat cold water in the water heater before you take a shower. One way or the other, you are using up energy someplace. Or is that not the point.
PS. Drain the water tank every year. Change the furnace filter twice a year. Change the oil in your car every 3–5000 miles. Bathe once a day.

Dr_Lawrence's avatar

I boil cold filtered water from the tap in my stovetop kettle which has no accumulated scale or minerals, even after years of use.

JLeslie's avatar

Back in the day the old pipes would leach more bad stuff with hot water running through them so it was a given that water used for drinking or cooking should be cold from the pipes, but for bathing the hot was fine. Our newer pipes it doesn’t matter.

Unless that is an old wives tale. But, I actually do think it is true.

Edit: I found this seems old pipes were Lead, and even copper pipes were joined with lead and the hot water put more lead into the water so people were told to run water if the pipes had not been used for many hours and not to drink or cook with hot water because more lead wound up in that water. Guess it wasn’t an old wives tale.

SavoirFaire's avatar

Cold water does not boil faster than hot water. Hot water occasionally freezes faster than cold water.

For those who don’t want to click on the link:

Cold water absorbs heat faster than hot water, but it has more heat to gain before reaching boiling point. And once it becomes hot, it will absorb heat at the same rate as any other body of hot water under the same conditions. In other words, boiling cold water involves both the process of making the cold water hot and the process of making the hot water boil. Thus it is not possible for it to take less time than boiling hot water, which only involves one of these processes.

Hot water will only freeze faster than cold water in very special conditions in which convection figures. Cold water will slowly lose heat and more or less freeze all at once, whereas hot water can be made to freeze in layers. Thus a portion of the hot water will freeze before any of the cold water. Hot water will sometimes freeze faster than warm water if the hot water is hot enough that it is losing mass while also losing energy (thus reducing the amount of water that needs to freeze). Note that this happens because mass is not kept constant.

If you want clearer and/or more technical answers than that, you’re going to have to click on the link.

Coloma's avatar

@josie Would you like to be my house boy? I can bathe myself without help but you can make sure my towel is warm and fluffy. lol
@SavoirFaire Good explanation!
@Pandora Interesting, thanks!

Well…who’d have thought I’d get an entire course in the physics of water boiling and draining my water heater. Now where’s my giant list of to do stuff.

longgone's avatar

Um. Okay…well, @Coloma , you will need a pan. Fill with water, and then set on a surface you can heat. A radiator will not be sufficient, though. Most use a stove. If you have carefully followed all the steps, you will soon appreciate bubbling, hot H 2 O. Congratulations! Enjoy!

Earthgirl's avatar

@JLeslie That is the reason I have always heard as well. If you’re not sure about your pipes, better safe than sorry.

Coloma's avatar

@longgone Haha…well..I was really just curious about the science of bringing hot vs. cold water to a boil, but thanks and welcome to the pod. :-)

longgone's avatar

Truth be told, if you were incapable of boiling water I’d worry about letting you near any stoves at all… ;)
And interesting topic, by the way, I learned a lot!

Coloma's avatar

@longgone Well, being a left handed, right brained blonde I do have my challenges. Do not give me a sharp knife and have me go into Ginsu chef mode after a glass or three of wine. lol
Also, never, ever, let me play with matches or light candles when wine is involved. haha

longgone's avatar

Hm. Not accepting any dinner invitations from you, I think… ;)

Skaggfacemutt's avatar

You guys are all so smart! It is true, the only reason we are told to cook with cold water is because it is cleaner, not having sat in the water tank.

RealEyesRealizeRealLies's avatar

I wish water boiled as fast as my XXX wife made my blood boil. Talk about a renewable energy…

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