Hypoxia and Medicine

Why it take longer to boil water at high altitudes. why does air rise , cool and expand? Why is it really cold?

In the text book it says that temperature and pressure have an inverse relationship when it comes to altitude. It says that as air goes up in altitude the pressure decreases and the temperature increases. Why it take longer to boil water at high altitudes. why does air rise , cool and expand? Why is it really cold at higher altitudes?

Public Comments

1. google it dude... :]
2. The boiling point of water rises as the altitude, so for example if you were on a plane, it would boil maybe at 103 celcius, but underwater in a submarine it would boil at maybe 97 celcius. Ok....maybe I didn't really help Edit: Ok sorry, I mixed them both up, other way round
3. It actually boils at altitude QUICKER but it does at less temperature. Say at 10,000 ft water might boil at 170F instead of 212F. So you have to boil the water longer to cook something or kill germs because the heat of the boil is so much less. It boils easier at 10,000 ft because of the low air pressure outside. The water in effect has a vacuum on it compared to sea level so the water compound can leave the surface a lot easier into this low pressure. The opposite happens if you raise pressure. That is how a pressure cooker works. If you allow the exterior pressure to increase, the water can't leave the surface so the pressure continues to build until it is greater than the surface pressure Air rises from heat, but it also becomes less dense because of this heat. So if you started out with a cubic foot of air and then heated it at sea level until it became 5 cubic feet, then each of those 5 cubic feet only has 1/5 of the amount of air molecules in it. So the air rises because it is less dense than sea level air and rises until it gets to the height where the air is 1/5th the density of air at sea level and then the air can't rise any more because it is same density at altitude. It is cold at altitudes because heat is only contained in solid molecules. The higher you go, the less air molecules there are to hold onto heat. Plus heat is radiant energy and the radiance leaves the particles of air if new radiant heat isn't constantly added to the thinner air. But at altitude, even when the sun is shining, it feels colder simply because there is less air molecules around you that hold heat so it feels colder. But you will notice even when it is freezing outside at altitude, the sun still makes a solid like your face feel warm because it delivers the radiant heat to a dense surface . Once the sun goes down there is no new radiant heat added and the few air molecules at altitude now radiant their heat out which a lot is lost to space and because the thermal mass of thin air is so much less than sea level air, it gets cold much quicker at altitude. Space has no air, but you can't really feel the cold, because there is no mass to retain that cold. So as long as a astronaut wears reflective clothing, his own heat will be re-reflected back to him instead of being lost to space. If he went out in space without a suit, it would only feel cold because his radiant heat goes straight out to space and is not reflected back to him. On a mountain top it actually feels colder, because of the thin air. The thin air might contain real low levels of radiant heat , so when you are in that atmosphere, the thin cold air, draws heat away from your body much quicker at zero C at altitude, than at space where the temperature might be -270C. Because there is nothing in that cold space to draw heat from you. You are basically living in the vacuum portion of a thermos bottle, where only thermal radiant energy can traverse, not conduction heat