Does temperature increase when water is boiling at 100C......

[Carbon273]

Does temperature increase when water is boiling at 100C in a closed system? I am picturing a scenario where I am boiling water in a pot to make pasta. However, I decide to close the pot as the water is still boiling. By doing this I am sealing away the system of study from the environment. Thus making it a closed system with fixed boundaries. As the saturated liquid and saturated vapor conditions coexist in the system, does the temperature increase the system prematurely? If not, then how would this differ from having the pot boil with the lid removed?

The reason why I asked this is because I believe pressure plays a distinct role in both scenarios. Where the latter, atmospheric pressure is present and the former the pressure is encapsulated and thus contributes to the temperature increasing possibly prematurely. Just looking for clarification.

 

[AZFIREBALL]

First off - What you described is not a closed system. A closed system allows for NO leakage. Putting a cover on the pot does not prevent the steam from escaping. In the scenario you describe, the temperature will remain at 100 C for as long as there is water in the pot

 

[scottdave]

Yes the temperature which water boils depends on the pressure. Here is a phase diagram for water.

https://goo.gl/images/kPzjSN

 

[Carbon273]

First off - What you described is not a closed system. A closed system allows for NO leakage. Putting a cover on the pot does not prevent the steam from escaping. In the scenario you describe, the temperature will remain at 100 C for as long as there is water in the pot

hmmm interesting. So let's say, that hypothetically, we are viewing a closed system. A case where no leakage occurs whatsoever. What will happen then? For both cases where the there is an adiabatic process and there isn't one. Sorry for adding more questions on top of my initial one, I am genuinely curious.

 

[Nik_2213]

'Closed' system ? That's a 'pressure cooker'.
https://en.wikipedia.org/wiki/Pressure_cooking
As the pressure rises initially, boiling will reduce until the water is further heated. Then, as pressure builds, the regulator valve lifts or the safety pop blows...

FWIW, in addition to 'flat top' and 'hi top' metal versions for hobs, there are simplified plastic versions suitable for microwaves...

 

[jrmichler]

If you have a closed system with water and heat, then the pressure will rise until something happens:
1) You might get lucky and the pressure will rise until heat loss equals heat added.
2) Or something will open and release the pressure.
2A) If you are lucky, a relief valve will open and vent the pressure.
2B) If you are not lucky, search water heater explosion or boiler explosion. There is an excellent Mythbuster's video online.

Back in the 1800's, boiler explosions were common, as were the resulting deaths. That resulted in the ASME Boiler and Pressure Vessel Code, which specifies safety factors, design practices, materials, and relief valves.