boiling water? high altitudes?

[tommo123]

water boils at lower temps at higher altitudes right? so up these mountains, if you wanted a cup of tea/coffee you could get a boiling hot cup - but the boiling point would be lower than 100C?

is that right?

 

[Corrode]

Yes, it depends on atmospheric pressure. BTW check this calculator out. It will calculate it for you.

 

[biostud]

Yes, and for the same reason it's good to have a pressure cooker if you live at high altitudes. Otherwise cooking can take very long time.

 

[Jeff7]

As pressure drops, the temperature required to boil water goes down. Drop the pressure low enough, and it would boil at room temperature.

 

[biostud]

Yes, it depends on atmospheric pressure. BTW check this calculator out. It will calculate it for you.

....if you use this then the boiling temperature of water reaches absolute zero as you move towards vacuum. So water in vacuum will boil instead of freeze?

 

[biostud]

heres a nice video were they boil and freeze water at room temperature.
http://www.youtube.com/watch?v=yW5UeJtXxYA

 

[Corrode]

Not water but teritiary alcohol triple point video, looks cool
http://www.youtube.com/watch?v=BLRqpJN9zeA

 

[tommo123]

thanks for those links, went youtube surfing for more sodium acetate and ferrofluid vids!

awesome vids

 

[Tuna-Fish]

....if you use this then the boiling temperature of water reaches absolute zero as you move towards vacuum. So water in vacuum will boil instead of freeze?

Some of it will boil, some of it will freeze. Vacuum isn't cold, it's just a very good insulator. If you place a hard object in vacuum, it won't become any colder or warmer. However, the act of boiling removes heat from the remaining liquid. So, if you take a glass of water and dump it into vacuum, it will instantly start boiling. This boiling will reduce it's temperature, quickly making some of it start to freeze. This will go on until there is no liquid left, just ice and water vapor.

 

[biostud]

Some of it will boil, some of it will freeze. Vacuum isn't cold, it's just a very good insulator. If you place a hard object in vacuum, it won't become any colder or warmer. However, the act of boiling removes heat from the remaining liquid. So, if you take a glass of water and dump it into vacuum, it will instantly start boiling. This boiling will reduce it's temperature, quickly making some of it start to freeze. This will go on until there is no liquid left, just ice and water vapor.

yeah, I found out looking at the video in my later post

 

[silverpig]

Some of it will boil, some of it will freeze. Vacuum isn't cold, it's just a very good insulator. If you place a hard object in vacuum, it won't become any colder or warmer. However, the act of boiling removes heat from the remaining liquid. So, if you take a glass of water and dump it into vacuum, it will instantly start boiling. This boiling will reduce it's temperature, quickly making some of it start to freeze. This will go on until there is no liquid left, just ice and water vapor.

I've seen this happen with liquid nitrogen when we put it in a vacuum chamber. It starts as a liquid, then as the pressure drops it freezes. When you increase the pressure again, it melts.

 

[DirkGently1]

You can't make a good cup of tea at high altitudes. Not without a pressure cooker anyway.

 

[Murloc]

for pasta it's a reverse situation: at sea it's more difficult to avoid overcooking it.

 

[WildHorse]

OP you have it backwards, IF you're thinking of the TIME rather than the TEMP.

It's a PITA to boil water at high altitude. Takes forever, and consumes way too much precious campsove fuel.

At lower atmos, it takes LONGER to oil water.

 

[bendixG15]

Mountain explorers in the good old days used to determine their elevation on the mountain by boiling water.

 

[PsiStar]

OP you have it backwards, IF you're thinking of the TIME rather than the TEMP.

It's a PITA to boil water at high altitude. Takes forever, and consumes way too much precious campsove fuel.

At lower atmos, it takes LONGER to oil water.

This makes no sense at all ... 2 conflicting statements.

 

[bunnyfubbles]

OP you have it backwards, IF you're thinking of the TIME rather than the TEMP.

It's a PITA to boil water at high altitude. Takes forever, and consumes way too much precious campsove fuel.

At lower atmos, it takes LONGER to oil water.

I think you have things a bit confused, it takes less time to get the water to boil at high altitude but more time to cook because the water boils at a lower temperature

 

[WildHorse]

This makes no sense at all ... 2 conflicting statements.

Don't understand your remark. What do you think are conflicting statements?

At higher elevation, atmospheric pressure is less, and it takes a longer time per BTU to boil water, compared to same at sea level. Trust me!

 

[Red Squirrel]

Interesting concept. So with this, would it be possible to make a sun powered air conditioning or water cooling/freezing system?

Basically use the sun to boil water, this water is then subjected to a vacuum and freezes. I guess the energy required to produce the vacuum is probably very high though, or is it? Like, would an air compressor (hooked from the inlet obviously) do it, or do you need much more suction power?

 

[Lemon law]

Its not hard to understand at all, if we realize its all about the four various states of matter. There is the plasma state, the gas state, the liquid state, and the solid state. And if you want quibble, we can add nuclear transformations too. But if we want to restrict the question to normal earth conditions that make life as we know it possible, we can somewhat eliminate the plasma and nuclear questions.

Depending on the chemistry of the atomic and molecular states mixtures in question, we can get wildly different results as we vary temperature and pressure. ( and its hard to talk about H20 here because its a rather nonstandard behaving non-conventional liquid. )

But as soon as we talk only about the solid, or gas, or liquid question, we have to immediately ask, why should any given atom, stick to any other another, regardless if they all have the same number or protons in their nucleus or not. And we can only explain it with the behavior of electrons between two of the same or different atomic numbers atoms.

In a pure gas, the inter atomic attraction is zero, although we have many gases that bond together and gain a tiny bit of energy as say two nitrogen atoms stick together to become N2, or two Oxygen atoms become O2. They still act like a gas that will get ever further apart in a vacuum, or can be packed ever tighter by adding pressure.

But the liquid state of matter is quite a different State, suddenly its gains lots of energy
as it packs to minimum volume and can't become smaller with the addition of pressure. But still liquids can assume any shape, and can be poured from one container to another of different shape. Only volume must be conserved.

The we can talk about the solid state where even more energy is gained as it preserves both of its volume and its shape. And suddenly we can ask how hard, soft or brittle it is? At least until recently, the conventional solid state thinking was confined to saying, there are only a limited number of ways metals could crystallize in, known 3000 years ago by the Greeks, and now the recent Nobel in Chemistry has been given to an out of the box thinker who has proved not even that is always true.

But still getting away from the liquid to gas boiling point question. Because the key to understanding that is in statistics and molecular. Why should we assume that all atoms in a mixture are going at the same velocity even if the overall mixture is stable in temperature, especially in a liquid. Because all the atoms are always banging against each other, many many times every second. Some slow to almost zero in a collision and have a temporary temp of absolute zero, and other speed up and have a far higher temperature. In other words, for any given atom, temporary velocity equals temperature. Which means at any given time every atom might have sufficient velocity to tear apart its attraction to its neighbor it was stuck to before. Now if we apply that to a pot of water at some altitude being heated from below, we can finally understand what is happening. Because those temporary higher velocity water molecules at the air liquid interface have a far higher probability of escaping the water in the pot, and becoming just a gas in our atmosphere. Its a meta stable reaction rate, how many water molecules that escape the mixture compared to how many slow down and join back up with a another similar water molecule before escaping the mixture.

And that also explains why all those free H2O water molecules in our atmosphere later join up and fall as rain, and or snow when temperature and pressure change.

 

[tynopik]

At higher elevation, atmospheric pressure is less, and it takes a longer time per BTU to boil water, compared to same at sea level. Trust me!

yes, no, no

 

[Mr. Pedantic]

Don't understand your remark. What do you think are conflicting statements?

At higher elevation, atmospheric pressure is less, and it takes a longer time per BTU to boil water, compared to same at sea level. Trust me!

It's hard to trust someone who's wrong.

 

[WildHorse]

It's hard to trust someone who's wrong.

Yet I'm a very very very veteran backpacker. Literally hundreds, it's one of my things, back to nature & all.

I've cooked literally hundreds (probably thousands) of times in the California High Sierra mountains at high altitude, and in the Swiss Alps and the in the New Zealand Southern Alps. Some future day... Himilayas!

Trying to get that friggin water to boil so we can have a non-giuardia drink is a real PITA, all the while concerned about conserving that fuel.

I've had to cut backpack trips short solely because we ran out of fuel trying to boil water at >11,700+ feet
(kersarge pass
and another
and another
and another )

I'm pretty sure, based on experience, that I'm right in what I posted.

 

[edcarman]

Basic thermodynamics says that it will take less energy and, with a constant heat source, less time to boil room temperature water at higher altitudes.

On the other hand, at higher altitudes, the starting temperature of the water may be lower due to colder ambient conditions. The reduced pressure and lower oxygen content may also make the burner on the stove less efficient, meaning you need more fuel to produce the same amount of heat energy and that heat is produced at a lower rate.

Both of the above could mean it takes longer and requires more fuel to boil the water.

 

[CycloWizard]

Oxygen concentration in the air is inversely proportional to the altitude, just like pressure (in other words, oxygen concentration is proportional to the pressure). Flame temperature and heat output depend on oxygen concentration. Thus, while the energy requirement may be less for boiling water, it can also take longer.