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Name: steve
Status: other
Age: 30s
Location: N/A
Country: N/A
Date: 2000-2001


Question:
water will not boil in Colorado or maybe Wyoming because of high altitudes & potato chip bags burst in shipment due to high pressure in those areas????im a trk/driver & have been told this for years & i wonder if there is such a place or issue where this is true?????myth / or fact


Replies:
Steve -

You are on the right track, but the info lost something in the retelling.

Because of the lower (not higher) atmospheric pressure, water boils at a lower temperature at higher altitudes. It is therefore more difficult to cook food in boiling water in Denver than in New Orleans. The boiling water will only reach... perhaps 96 degrees C instead of 100. Cooking times are longer. As far as your potato chip bags... yes, if they are sealed tightly at a lower elevation, the pressure differential at 6000 feet might cause them to explode. It is the same reason that when weather balloons are launched they do not appear to be full. As they climb, the gas inside the balloon expands.

Larry Krengel


Steve,

Water boils when the vapor pressure of water exceeds atmospheric pressure. At high elevations (such as Colorado or Wyoming) it boils at lower temperatures because the atmospheric pressure is LOWER at high elevations. Because the boiling temperature is lower at high elevations foods that are cooked by boiling take a little longer to cook at high elevation.

Certainly potato chip bags will swell as they are taken to higher elevations (because the amount of gas in the bag is fixed but the pressure outside is reduced, the gas inside will swell the bag against the reduced atmospheric pressure). Whether they will burst will depend on how strong the bags are. Usually the weakest point will be the seams of the bags. It is quite likely that at least some of the bags will burst at the seams if they are trucked from low altitude over the continental divide.

Bradburn


Atmospheric pressure decreases significantly the higher the elevation -- a lot of other things being equal. So high up in the Rocky Mountains water boils at a temperature less than 100 C [212 F], but it still boils when the pressure of the water vapor equals the atmospheric pressure.

I never heard of potato chip bags actually bursting, but if they are packaged under a positive pressure of some inert gas like nitrogen to exclude oxygen that could turn the oil rancid, I suppose they could burst because the pressure of the atmosphere exerted on the bag becomes sufficiently lower than the inert gas pressure inside the bag so that the internal pressure exceeds the bursting strength of the bag.

Vince Calder


I used to live at a reasonably high altitude (7200 ft) in New Mexico, and I can tell you that there IS a grain of truth to what you have heard.

First of all, water WILL boil at high altitudes, but it isn't as hot as boiling water at sea level. This is because the air pressure is LOWER at high elevations. Boiling occurs when the water is hot enough to have the same pressure as the surrounding air, so that it can form bubbles. As water is heated, its steam pressure rises, until it reaches the pressure of the surrounding air. At high altitudes, this air pressure is lower than at sea level, so the water doesn't have to get so hot to get to boiling. Because the temperature of the boiling water is lower at high elevations than at sea level, it takes longer to cook things, such as eggs, potatoes, or spaghetti, at high altitudes than at sea level.

At high altitudes, things like potato chip bags can burst. This is because they were sealed at low altitude where the air pressure was high, and their internal pressure is thus the pressure of the air where they were sealed. At high altitudes, the pressure inside the bag is still the same as sea level air pressure, but the air pressure outside the bag is lower. This means that overall the air inside the bag pushes outward harder than the air outside the bag pushes inward. Sometimes this difference is enough to cause the bag to fail.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois



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