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Q & A: water temperatures

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Most recent answer: 06/14/2018
Q:
Is it true that water (steam and ice) can not get hotter than 212 degrees and colder than 32 degrees?
- Tommy
Seattle
A:
It is not true that water can only get up to 212 degrees and as cold as 32 degrees. After water changes from a liquid to a gas (at 212 degrees Fahrenheit) it can actually heat up much hotter than that. In the gas form, water molecules are spread out and have a lot of room to move and get much hotter than the other two phases (liquid and ice).
And water freezes at 32 degrees Fahrenheit. But it can actually get colder than that, all the way toward what we call absolute zero. This value is equivalent to about -459 degrees Fahrenheit. This is when the water molecules are basically not moving. Hope this answers your question!

(but see below- if the question concerns liquid water, it becomes unstable outside the temperature range mentioned, at atmospheric pressure. Mike W.)

(published on 10/22/2007)

Follow-Up #1: boiling and superheating

Q:
but what about the water itself water will only get to 212 then turn to a gas unless water is in a pressure cooker the water cannot get above 212, or am i wrong?
- Dan
wapakoneta,oh,us
A:
You’re sort of right. Above 212°F at standard pressure, liquid water is unstable. It will evaporate very rapidly from the surface. If the temperature is held constant (which requires some heat input, since evaporation cools things) the liquid will all evaporate.
If the temperature is much above 212°F, the water will boil. That means that it won’t just evaporate from the surface but will form vapor bubbles, which then grow, inside the liquid itself. If the water has very few dust flecks etc. in it, this boiling process doesn’t happen until the temperature is significantly above 212°F, so you can temporarily have liquid water (called ’superheated’) above that boiling point. If there are good nucleation sites for the boiling to start (teflon surfaces are a good example) you can’t get much superheating.

you might search this site and others using the key word ’superheated’.

Mike W.

Lee H

(published on 10/22/2007)

Follow-Up #2: superheating?

Q:
OK, but why then does liquid water open to the atmosphere continue to boil for a few moments after the heat source is removed? Is it just due to residual heat
- Andy (age 68)
SLC, UT, USA
A:

The water can be somewhat superheated, as we mentioned. Also, by the time the water is boiling the pot will be hotter than 212°F, so heat from it flows in to boil some more water. 

Mike W.


(published on 04/17/2017)

Follow-Up #3: water at 6500 °F?

Q:
So can u explain to me how water is able to stay in a environment with a 6500 Fahrenheit temperature and not evaporate!? Cuz I'm lost on that and how that makes any sense what so ever? And rely wanna know the answer to that one cuz I get told I'm stupid for asking that question
- Craig Godfrey (age 33)
Rimbey Alberta
A:

I have no idea how liquid water could exist at that temperature. It's far above the "critical point" at which the distinction between gas and liquid is lost. I'm pretty sure that at that high temperature water molecules mostly fall apart, so you really wouldn't have water at all.

Mike W.


(published on 08/29/2017)

Follow-Up #4: water at 212°F

Q:
What does water do at 212 degrees Fahrenheit
- Kyah (age 10)
A:

It boils.

Mike W.


(published on 11/01/2017)

Follow-Up #5: temperature of ice and water

Q:
My Chemestry textbook states that liquid water boils (regardless of how rapidly it's boiling) at 100 degrees C. It goes on to say that ice water (regardless of the amount of ice mixed with water) is always 0 degrees. Is water in solid form always 0 degrees C? If I stick ice in a -15 C freezer, will the tempature of the ice drop? Or will it stay 0 degrees C? So to test this, I filled a glass with ice, and then added enough water to float the ice. My thermometer reads 0 degrees C at the bottom of the glass, where the water is. But, at the top, in the midst of the floating ice, it says -1 C. If my texbook is right, shouldn't it have been 0 degrees C, no matter where the thermometer was? What went wrong? I'm struggling to understand this concept, so any explantion would be highly appreciated! Note: It boiled at 96 C, but i'm assuming this is becuase of atmospheric pressure.
- Natasha R. (age 17)
A:

Ice can certainly be much colder than 0°C. Even liquid water can be a bit colder than 0°C for a while, until it manages to find its way to the crystalline ice state. We discuss that a lot on this site under the name "supercool".

Usually when you stick the water in the cold freezer it will cool just a little past 0°C, then hang up near 0°C until all the water has turned to ice, then continue cooling until it reaches the freezer temperature. If the water is unusually free of dust, etc. it may supercool pretty far below 0°C before the freezing starts.

Mike W.


(published on 01/29/2018)

Follow-Up #6: vapor pressure

Q:
How is there water vapor in the air when it is not at least 100 degrees Celsius? I�ve heard people say that this is because the water isn�t actually a vapor. If that is the case, how is a liquid floating in the air?
- Eli Tatum (age 19)
Alabama
A:

Even below 100°C, some water molecules will escape from the liquid and go into the vapor. Equilibrium is reached when their concentration (the density of the water vapor) is high enough so that the rate of molecules coming back from the vapor and rejoining the liquid just balances the rate at which they leave. These molecules in the vapor are truly in the gas phase, not contacting each other much. 

So what's different at 100°C? Above 100°C the molecules leave the liquid so fast that equilibrium could only be reached with water vapor so dense that its pressure would be higher than ordinary atmospheric pressure. So at atmospheric pressure, all the water molecules leave the liquid and join the gas. Below 100°C, only some do, at least in a closed container.

Mike W.


(published on 06/14/2018)

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