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Subject:
Physics: water boiling at altitude?
Category: Science > Physics Asked by: tucker5-ga List Price: $2.00 |
Posted:
01 Jan 2003 20:56 PST
Expires: 31 Jan 2003 20:56 PST Question ID: 136256 |
Does it take longer to bring water to 212 degrees Fahrenheit at 6200 feet altitude? And what is the relationship between the water bubbling at altitude and the temperature of the water? |
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Subject:
Re: Physics: water boiling at altitude?
Answered By: hedgie-ga on 06 Jan 2003 08:36 PST |
Hi tucker Both comments are good and useful, but your question is not wrong: Not only customer is never wrong, but also from point of view of logic answer is possible: It takes longer, indeed infinitely long, since all your water evaporates before reaching 212 F. Unless you use sparkys idea, in which case it is the time to handle the cooker :-). Seriously, To get Boiling Point (temperature when water starts bubling) at given altitude take away .9 F for each 500 feet increase in altitude. http://www.fetco.com/boilingpoint.htm for 6000 feet you get 200 - 201 F. (depending on weather) More details at: http://newton.dep.anl.gov/askasci/phy00/phy00252.htm hedgie |
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Subject:
Re: Physics: water boiling at altitude?
From: socal-ga on 02 Jan 2003 01:08 PST |
Hi You are slightly wrong in the way you posed the question, since you ask "why does it take LONGER to reach 212 F (boiling at sea level) at higher altitudes?" Your actual question should be "Why does boiling water not reach 212 F at high altitudes." The rate of temperature increase is the same at all altitudes. However, the water temperature will not go above the boiling temperature at that altitude, which decreases as the altitude increases and the air pressure decreases. "Boiling" occurs at the temperature where the water has enough energy to vaporize at that air pressure. The converse is the fact that water does not boil at sea level, if a pressure cooker is used to increase the air pressure. At lower air pressures (higher altitudes) water will boil at lower temperatures, and thus food takes longer to cook if boiled at higher altitudes. |
Subject:
Re: Physics: water boiling at altitude?
From: sparky4ca-ga on 03 Jan 2003 19:16 PST |
Socal basically has it. The higher above sea level you go the lower your air pressure is. The lower below sea level you go, the higher your air pressure is. The lower the air pressure, the lower the temperature at which water boils. The higher the air pressure, the higher the remperature at which water boils. Water cannot be heated past the boiling point as it turns to steam at the boiling point. (Although I have been told that you can get turbo cookers that heat water up faster then it can convert to steam, so for a brief time it would be hotter then the boil point.) This is something I read about when I got into home canning and preserves. Since at higher levels the water is still cooler even though it is boiling, it takes longer to process jars of preserves in the hot water bath. Also, since low-acid foods such as vegetables and meats have to be cooked to 240 degrees F to kill botulism, at sea level thesejars have to be cooked in a pressure cooker set to at least 10 pounds pressure. This allows the water to boil at, and create steam at, 240 degrees or higher. The higher above sea level, the higher the pressure needs to be in the pressure cooker to attain this. If you wanted to save time, and maybe some energy, at your 6200 foot altitude, use a pressure cooker, to cook foods faster and hotter. Just a suggestion. sparky4ca-ga |
Subject:
Re: Physics: water boiling at altitude?
From: anduril-ga on 24 Jan 2003 07:37 PST |
It is in fact possible for water to be super-heated past boiling point whilst still remaining liquid. We observe this when water is heated by microwave in a very smooth-surfaced container. When the container filled with hot water is removed from the microwave and (say) coffee is added, the water can -- literally -- explode as steam. The moral would seem to be: be careful when you microwave water for hot drinks! Anduril-ga |
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