What exact difference does pressure make?
A mountaineer is cooking potatoes at an altitude of 5,000 meters. He's surprised that the potatoes are still not cooked after 40 minutes of cooking. His wife is cooking in a pressure cooker. This pot is sealed with a pressure-tight lid. This reduces the cooking time to 10 minutes instead of the usual 30 minutes. What caused the cooking times to increase or decrease?
That's the question. I know it has something to do with the fact that there's less pressure at altitude (a vacuum) and more pressure in a pressure cooker. And also that vacuum and overpressure affect things like boiling points. But I can't seem to put all that together. So what exactly happens to the potatoes in the vacuum/overpressure?
Thank you very much for your help!
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Higher than the boiling point, you do not get the water heated. For this, you should first evaporate all water and then heat the steam further.
And the boiling point is logically dependent on atmospheric pressure. The lower this pressure, the lighter (i.e. with less energy, i.e. with less heat) molecules can dissolve from their siblings and froze only through the area. What you know as victories.
Low air pressure means lower boiling point. And with a lower temperature you can reach.
And maybe you’ve heard that chemical reactions with a cooling of 10 Kelvin are only half as fast…
Or, if you have a pressure cooker, you can also reach a higher boiling point thanks to the higher pressure, i.e. a higher temperature, so everything goes faster… twice as fast if you make a warming of 10 K.
The boiling temperature of the water should be between 80 and 85° C. at 5,000 m above sea level (details depending on the geographical width and weather), which is estimated to extend the boiling temperature by a factor of four to five.
I wrote a little about the relationship between sea height and boiling temperature in the face of a journey in the Himālaya and that in my travel blog hurried. There is also a form where you can calculate the temperature of the boiling water for a height you choose.
At lower pressure, the water thus boils faster at 5,000 m at 80° C. and thus the cooking time is extended.
The water already boils at lower temperatures at less pressure, so the water is not so hot as the energy is used for evaporation.
Dirlet doesn’t make the pressure difference. The pressure determines at which temperature the water boils, i.e. cooks. The higher the pressure, the higher the boiling temperature. We all know a value by heart: with normal air pressure of 1 bar, the water cooks at 100°C. All other boiling temperatures at other pressures must be checked in the steam pressure curve:
The potatoes are cooked with the respective boiling temperature. The lower this temperature, the longer it takes until they are soft and the higher the temperature is, the faster they are soft.
In short, with increasing pressure the boiling temperature increases and with increasing boiling temperature the potatoes become softer faster.
See here:
Hello! If a liquid wants to boil, it must expand. The weight of the atmosphere – i.e. air – works against it. The higher the location, the shorter the air column above it and the lower the back pressure. In space, your blood would boil immediately without spacesuit – 0 pressure
Let’s go to the extreme and cook eggs up. On high mountains as well as on Mount Everest, the egg yolk would germinate, but not the surrounding egg clear – thus does not work.
Water cooks on the Everest at approx. 70 degrees Celsius – never enough.
Years ago I found in Switzerland that an egg needs much more time to cook. Our egg watch no longer fits
Good evening